Index: imaps-frontend/node_modules/neo-async/async.js
===================================================================
--- imaps-frontend/node_modules/neo-async/async.js	(revision 79a03170cdde4e801d12257ee86723774970427b)
+++ imaps-frontend/node_modules/neo-async/async.js	(revision 79a03170cdde4e801d12257ee86723774970427b)
@@ -0,0 +1,9184 @@
+(function(global, factory) {
+  /*jshint -W030 */
+  'use strict';
+  typeof exports === 'object' && typeof module !== 'undefined'
+    ? factory(exports)
+    : typeof define === 'function' && define.amd
+    ? define(['exports'], factory)
+    : global.async
+    ? factory((global.neo_async = global.neo_async || {}))
+    : factory((global.async = global.async || {}));
+})(this, function(exports) {
+  'use strict';
+
+  var noop = function noop() {};
+  var throwError = function throwError() {
+    throw new Error('Callback was already called.');
+  };
+
+  var DEFAULT_TIMES = 5;
+  var DEFAULT_INTERVAL = 0;
+
+  var obj = 'object';
+  var func = 'function';
+  var isArray = Array.isArray;
+  var nativeKeys = Object.keys;
+  var nativePush = Array.prototype.push;
+  var iteratorSymbol = typeof Symbol === func && Symbol.iterator;
+
+  var nextTick, asyncNextTick, asyncSetImmediate;
+  createImmediate();
+
+  /**
+   * @memberof async
+   * @namespace each
+   * @param {Array|Object} collection
+   * @param {Function} iterator
+   * @param {Function} callback
+   * @example
+   *
+   * // array
+   * var order = [];
+   * var array = [1, 3, 2];
+   * var iterator = function(num, done) {
+   *   setTimeout(function() {
+   *     order.push(num);
+   *     done();
+   *   }, num * 10);
+   * };
+   * async.each(array, iterator, function(err, res) {
+   *   console.log(res); // undefined
+   *   console.log(order); // [1, 2, 3]
+   * });
+   *
+   * @example
+   *
+   * // array with index
+   * var order = [];
+   * var array = [1, 3, 2];
+   * var iterator = function(num, index, done) {
+   *   setTimeout(function() {
+   *     order.push([num, index]);
+   *     done();
+   *   }, num * 10);
+   * };
+   * async.each(array, iterator, function(err, res) {
+   *   console.log(res); // undefined
+   *   console.log(order); // [[1, 0], [2, 2], [3, 1]]
+   * });
+   *
+   * @example
+   *
+   * // object
+   * var order = [];
+   * var object = { a: 1, b: 3, c: 2 };
+   * var iterator = function(num, done) {
+   *   setTimeout(function() {
+   *     order.push(num);
+   *     done();
+   *   }, num * 10);
+   * };
+   * async.each(object, iterator, function(err, res) {
+   *   console.log(res); // undefined
+   *   console.log(order); // [1, 2, 3]
+   * });
+   *
+   * @example
+   *
+   * // object with key
+   * var order = [];
+   * var object = { a: 1, b: 3, c: 2 };
+   * var iterator = function(num, key, done) {
+   *   setTimeout(function() {
+   *     order.push([num, key]);
+   *     done();
+   *   }, num * 10);
+   * };
+   * async.each(object, iterator, function(err, res) {
+   *   console.log(res); // undefined
+   *   console.log(order); // [[1, 'a'], [2, 'c'], [3, 'b']]
+   * });
+   *
+   * @example
+   *
+   * // break
+   * var order = [];
+   * var array = [1, 3, 2];
+   * var iterator = function(num, done) {
+   *   setTimeout(function() {
+   *     order.push(num);
+   *     done(null, num !== 2);
+   *   }, num * 10);
+   * };
+   * async.each(array, iterator, function(err, res) {
+   *   console.log(res); // undefined
+   *   console.log(order); // [1, 2]
+   * });
+   *
+   */
+  var each = createEach(arrayEach, baseEach, symbolEach);
+
+  /**
+   * @memberof async
+   * @namespace map
+   * @param {Array|Object} collection
+   * @param {Function} iterator
+   * @param {Function} callback
+   * @example
+   *
+   * // array
+   * var order = [];
+   * var array = [1, 3, 2];
+   * var iterator = function(num, done) {
+   *   setTimeout(function() {
+   *     order.push(num);
+   *     done(null, num);
+   *   }, num * 10);
+   * };
+   * async.map(array, iterator, function(err, res) {
+   *   console.log(res); // [1, 3, 2];
+   *   console.log(order); // [1, 2, 3]
+   * });
+   *
+   * @example
+   *
+   * // array with index
+   * var order = [];
+   * var array = [1, 3, 2];
+   * var iterator = function(num, index, done) {
+   *   setTimeout(function() {
+   *     order.push([num, index]);
+   *     done(null, num);
+   *   }, num * 10);
+   * };
+   * async.map(array, iterator, function(err, res) {
+   *   console.log(res); // [1, 3, 2]
+   *   console.log(order); // [[1, 0], [2, 2], [3, 1]]
+   * });
+   *
+   * @example
+   *
+   * // object
+   * var order = [];
+   * var object = { a: 1, b: 3, c: 2 };
+   * var iterator = function(num, done) {
+   *   setTimeout(function() {
+   *     order.push(num);
+   *     done(null, num);
+   *   }, num * 10);
+   * };
+   * async.map(object, iterator, function(err, res) {
+   *   console.log(res); // [1, 3, 2]
+   *   console.log(order); // [1, 2, 3]
+   * });
+   *
+   * @example
+   *
+   * // object with key
+   * var order = [];
+   * var object = { a: 1, b: 3, c: 2 };
+   * var iterator = function(num, key, done) {
+   *   setTimeout(function() {
+   *     order.push([num, key]);
+   *     done(null, num);
+   *   }, num * 10);
+   * };
+   * async.map(object, iterator, function(err, res) {
+   *   console.log(res); // [1, 3, 2]
+   *   console.log(order); // [[1, 'a'], [2, 'c'], [3, 'b']]
+   * });
+   *
+   */
+  var map = createMap(arrayEachIndex, baseEachIndex, symbolEachIndex, true);
+
+  /**
+   * @memberof async
+   * @namespace mapValues
+   * @param {Array|Object} collection
+   * @param {Function} iterator
+   * @param {Function} callback
+   * @example
+   *
+   * // array
+   * var order = [];
+   * var array = [1, 3, 2];
+   * var iterator = function(num, done) {
+   *   setTimeout(function() {
+   *     order.push(num);
+   *     done(null, num);
+   *   }, num * 10);
+   * };
+   * async.mapValues(array, iterator, function(err, res) {
+   *   console.log(res); // { '0': 1, '1': 3, '2': 2 }
+   *   console.log(order); // [1, 2, 3]
+   * });
+   *
+   * @example
+   *
+   * // array with index
+   * var order = [];
+   * var array = [1, 3, 2];
+   * var iterator = function(num, index, done) {
+   *   setTimeout(function() {
+   *     order.push([num, index]);
+   *     done(null, num);
+   *   }, num * 10);
+   * };
+   * async.mapValues(array, iterator, function(err, res) {
+   *   console.log(res); // { '0': 1, '1': 3, '2': 2 }
+   *   console.log(order); // [[1, 0], [2, 2], [3, 1]]
+   * });
+   *
+   * @example
+   *
+   * // object
+   * var order = [];
+   * var object = { a: 1, b: 3, c: 2 };
+   * var iterator = function(num, done) {
+   *   setTimeout(function() {
+   *     order.push(num);
+   *     done(null, num);
+   *   }, num * 10);
+   * };
+   * async.mapValues(object, iterator, function(err, res) {
+   *   console.log(res); // { a: 1, b: 3, c: 2 }
+   *   console.log(order); // [1, 2, 3]
+   * });
+   *
+   * @example
+   *
+   * // object with key
+   * var order = [];
+   * var object = { a: 1, b: 3, c: 2 };
+   * var iterator = function(num, key, done) {
+   *   setTimeout(function() {
+   *     order.push([num, key]);
+   *     done(null, num);
+   *   }, num * 10);
+   * };
+   * async.mapValues(object, iterator, function(err, res) {
+   *   console.log(res); // { a: 1, b: 3, c: 2 }
+   *   console.log(order); // [[1, 'a'], [2, 'c'], [3, 'b']]
+   * });
+   *
+   */
+  var mapValues = createMap(arrayEachIndex, baseEachKey, symbolEachKey, false);
+
+  /**
+   * @memberof async
+   * @namespace filter
+   * @param {Array|Object} collection
+   * @param {Function} iterator
+   * @param {Function} callback
+   * @example
+   *
+   * // array
+   * var order = [];
+   * var array = [1, 3, 2];
+   * var iterator = function(num, done) {
+   *   setTimeout(function() {
+   *     order.push(num);
+   *     done(null, num % 2);
+   *   }, num * 10);
+   * };
+   * async.filter(array, iterator, function(err, res) {
+   *   console.log(res); // [1, 3];
+   *   console.log(order); // [1, 2, 3]
+   * });
+   *
+   * @example
+   *
+   * // array with index
+   * var order = [];
+   * var array = [1, 3, 2];
+   * var iterator = function(num, index, done) {
+   *   setTimeout(function() {
+   *     order.push([num, index]);
+   *     done(null, num % 2);
+   *   }, num * 10);
+   * };
+   * async.filter(array, iterator, function(err, res) {
+   *   console.log(res); // [1, 3];
+   *   console.log(order); // [[1, 0], [2, 2], [3, 1]]
+   * });
+   *
+   * @example
+   *
+   * // object
+   * var order = [];
+   * var object = { a: 1, b: 3, c: 2 };
+   * var iterator = function(num, done) {
+   *   setTimeout(function() {
+   *     order.push(num);
+   *     done(null, num % 2);
+   *   }, num * 10);
+   * };
+   * async.filter(object, iterator, function(err, res) {
+   *   console.log(res); // [1, 3];
+   *   console.log(order); // [1, 2, 3]
+   * });
+   *
+   * @example
+   *
+   * // object with key
+   * var order = [];
+   * var object = { a: 1, b: 3, c: 2 };
+   * var iterator = function(num, key, done) {
+   *   setTimeout(function() {
+   *     order.push([num, key]);
+   *     done(null, num % 2);
+   *   }, num * 10);
+   * };
+   * async.filter(object, iterator, function(err, res) {
+   *   console.log(res); // [1, 3];
+   *   console.log(order); // [[1, 'a'], [2, 'c'], [3, 'b']]
+   * });
+   *
+   */
+  var filter = createFilter(arrayEachIndexValue, baseEachIndexValue, symbolEachIndexValue, true);
+
+  /**
+   * @memberof async
+   * @namespace filterSeries
+   * @param {Array|Object} collection
+   * @param {Function} iterator
+   * @param {Function} callback
+   * @example
+   *
+   * // array
+   * var order = [];
+   * var array = [1, 3, 2];
+   * var iterator = function(num, done) {
+   *   setTimeout(function() {
+   *     order.push(num);
+   *     done(null, num % 2);
+   *   }, num * 10);
+   * };
+   * async.filterSeries(array, iterator, function(err, res) {
+   *   console.log(res); // [1, 3];
+   *   console.log(order); // [1, 3, 2]
+   * });
+   *
+   * @example
+   *
+   * // array with index
+   * var order = [];
+   * var array = [1, 3, 2];
+   * var iterator = function(num, index, done) {
+   *   setTimeout(function() {
+   *     order.push([num, index]);
+   *     done(null, num % 2);
+   *   }, num * 10);
+   * };
+   * async.filterSeries(array, iterator, function(err, res) {
+   *   console.log(res); // [1, 3]
+   *   console.log(order); // [[1, 0], [3, 1], [2, 2]]
+   * });
+   *
+   * @example
+   *
+   * // object
+   * var order = [];
+   * var object = { a: 1, b: 3, c: 2 };
+   * var iterator = function(num, done) {
+   *   setTimeout(function() {
+   *     order.push(num);
+   *     done(null, num % 2);
+   *   }, num * 10);
+   * };
+   * async.filterSeries(object, iterator, function(err, res) {
+   *   console.log(res); // [1, 3]
+   *   console.log(order); // [1, 3, 2]
+   * });
+   *
+   * @example
+   *
+   * // object with key
+   * var order = [];
+   * var object = { a: 1, b: 3, c: 2 };
+   * var iterator = function(num, key, done) {
+   *   setTimeout(function() {
+   *     order.push([num, key]);
+   *     done(null, num % 2);
+   *   }, num * 10);
+   * };
+   * async.filterSeries(object, iterator, function(err, res) {
+   *   console.log(res); // [1, 3]
+   *   console.log(order); // [[1, 'a'], [3, 'b'], [2, 'c']]
+   * });
+   *
+   */
+  var filterSeries = createFilterSeries(true);
+
+  /**
+   * @memberof async
+   * @namespace filterLimit
+   * @param {Array|Object} collection
+   * @param {number} limit - limit >= 1
+   * @param {Function} iterator
+   * @param {Function} callback
+   * @example
+   *
+   * // array
+   * var order = [];
+   * var array = [1, 5, 3, 4, 2];
+   * var iterator = function(num, done) {
+   *   setTimeout(function() {
+   *     order.push(num);
+   *     done(null, num % 2);
+   *   }, num * 10);
+   * };
+   * async.filterLimit(array, 2, iterator, function(err, res) {
+   *   console.log(res); // [1, 5, 3]
+   *   console.log(order); // [1, 3, 5, 2, 4]
+   * });
+   *
+   * @example
+   *
+   * // array with index
+   * var order = [];
+   * var array = [1, 5, 3, 4, 2];
+   * var iterator = function(num, index, done) {
+   *   setTimeout(function() {
+   *     order.push([num, index]);
+   *     done(null, num % 2);
+   *   }, num * 10);
+   * };
+   * async.filterLimit(array, 2, iterator, function(err, res) {
+   *   console.log(res); // [1, 5, 3]
+   *   console.log(order); // [[1, 0], [3, 2], [5, 1], [2, 4], [4, 3]]
+   * });
+   *
+   * @example
+   *
+   * // object
+   * var order = [];
+   * var object = { a: 1, b: 5, c: 3, d: 4, e: 2 };
+   * var iterator = function(num, done) {
+   *   setTimeout(function() {
+   *     order.push(num);
+   *     done(null, num % 2);
+   *   }, num * 10);
+   * };
+   * async.filterLimit(object, 2, iterator, function(err, res) {
+   *   console.log(res); // [1, 5, 3]
+   *   console.log(order); // [1, 3, 5, 2, 4]
+   * });
+   *
+   * @example
+   *
+   * // object with key
+   * var order = [];
+   * var object = { a: 1, b: 5, c: 3, d: 4, e: 2 };
+   * var iterator = function(num, key, done) {
+   *   setTimeout(function() {
+   *     order.push([num, key]);
+   *     done(null, num % 2);
+   *   }, num * 10);
+   * };
+   * async.filterLimit(object, 2, iterator, function(err, res) {
+   *   console.log(res); // [1, 5, 3]
+   *   console.log(order); // [[1, 'a'], [3, 'c'], [5, 'b'], [2, 'e'], [4, 'd']]
+   * });
+   *
+   */
+  var filterLimit = createFilterLimit(true);
+
+  /**
+   * @memberof async
+   * @namespace reject
+   * @param {Array|Object} collection
+   * @param {Function} iterator
+   * @param {Function} callback
+   * @example
+   *
+   * // array
+   * var order = [];
+   * var array = [1, 3, 2];
+   * var iterator = function(num, done) {
+   *   setTimeout(function() {
+   *     order.push(num);
+   *     done(null, num % 2);
+   *   }, num * 10);
+   * };
+   * async.reject(array, iterator, function(err, res) {
+   *   console.log(res); // [2];
+   *   console.log(order); // [1, 2, 3]
+   * });
+   *
+   * @example
+   *
+   * // array with index
+   * var order = [];
+   * var array = [1, 3, 2];
+   * var iterator = function(num, index, done) {
+   *   setTimeout(function() {
+   *     order.push([num, index]);
+   *     done(null, num % 2);
+   *   }, num * 10);
+   * };
+   * async.reject(array, iterator, function(err, res) {
+   *   console.log(res); // [2];
+   *   console.log(order); // [[1, 0], [2, 2], [3, 1]]
+   * });
+   *
+   * @example
+   *
+   * // object
+   * var order = [];
+   * var object = { a: 1, b: 3, c: 2 };
+   * var iterator = function(num, done) {
+   *   setTimeout(function() {
+   *     order.push(num);
+   *     done(null, num % 2);
+   *   }, num * 10);
+   * };
+   * async.reject(object, iterator, function(err, res) {
+   *   console.log(res); // [2];
+   *   console.log(order); // [1, 2, 3]
+   * });
+   *
+   * @example
+   *
+   * // object with key
+   * var order = [];
+   * var object = { a: 1, b: 3, c: 2 };
+   * var iterator = function(num, key, done) {
+   *   setTimeout(function() {
+   *     order.push([num, key]);
+   *     done(null, num % 2);
+   *   }, num * 10);
+   * };
+   * async.reject(object, iterator, function(err, res) {
+   *   console.log(res); // [2];
+   *   console.log(order); // [[1, 'a'], [2, 'c'], [3, 'b']]
+   * });
+   *
+   */
+  var reject = createFilter(arrayEachIndexValue, baseEachIndexValue, symbolEachIndexValue, false);
+
+  /**
+   * @memberof async
+   * @namespace rejectSeries
+   * @param {Array|Object} collection
+   * @param {Function} iterator
+   * @param {Function} callback
+   * @example
+   *
+   * // array
+   * var order = [];
+   * var array = [1, 3, 2];
+   * var iterator = function(num, done) {
+   *   setTimeout(function() {
+   *     order.push(num);
+   *     done(null, num % 2);
+   *   }, num * 10);
+   * };
+   * async.rejectSeries(array, iterator, function(err, res) {
+   *   console.log(res); // [2];
+   *   console.log(order); // [1, 3, 2]
+   * });
+   *
+   * @example
+   *
+   * // object
+   * var order = [];
+   * var object = { a: 1, b: 3, c: 2 };
+   * var iterator = function(num, done) {
+   *   setTimeout(function() {
+   *     order.push(num);
+   *     done(null, num % 2);
+   *   }, num * 10);
+   * };
+   * async.rejectSeries(object, iterator, function(err, res) {
+   *   console.log(res); // [2];
+   *   console.log(order); // [1, 3, 2]
+   * });
+   *
+   * @example
+   *
+   * // object with key
+   * var order = [];
+   * var object = { a: 1, b: 3, c: 2 };
+   * var iterator = function(num, key, done) {
+   *   setTimeout(function() {
+   *     order.push([num, key]);
+   *     done(null, num % 2);
+   *   }, num * 10);
+   * };
+   * async.rejectSeries(object, iterator, function(err, res) {
+   *   console.log(res); // [2];
+   *   console.log(order); // [[1, 'a'], [3, 'b'], [2, 'c']]
+   * });
+   *
+   */
+  var rejectSeries = createFilterSeries(false);
+
+  /**
+   * @memberof async
+   * @namespace rejectLimit
+   * @param {Array|Object} collection
+   * @param {number} limit - limit >= 1
+   * @param {Function} iterator
+   * @param {Function} callback
+   * @example
+   *
+   * // array
+   * var order = [];
+   * var array = [1, 5, 3, 4, 2];
+   * var iterator = function(num, done) {
+   *   setTimeout(function() {
+   *     order.push(num);
+   *     done(null, num % 2);
+   *   }, num * 10);
+   * };
+   * async.rejectLimit(array, 2, iterator, function(err, res) {
+   *   console.log(res); // [4, 2]
+   *   console.log(order); // [1, 3, 5, 2, 4]
+   * });
+   *
+   * @example
+   *
+   * // array with index
+   * var order = [];
+   * var array = [1, 5, 3, 4, 2];
+   * var iterator = function(num, index, done) {
+   *   setTimeout(function() {
+   *     order.push([num, index]);
+   *     done(null, num % 2);
+   *   }, num * 10);
+   * };
+   * async.rejectLimit(array, 2, iterator, function(err, res) {
+   *   console.log(res); // [4, 2]
+   *   console.log(order); // [[1, 0], [3, 2], [5, 1], [2, 4], [4, 3]]
+   * });
+   *
+   * @example
+   *
+   * // object
+   * var order = [];
+   * var object = { a: 1, b: 5, c: 3, d: 4, e: 2 };
+   * var iterator = function(num, done) {
+   *   setTimeout(function() {
+   *     order.push(num);
+   *     done(null, num % 2);
+   *   }, num * 10);
+   * };
+   * async.rejectLimit(object, 2, iterator, function(err, res) {
+   *   console.log(res); // [4, 2]
+   *   console.log(order); // [1, 3, 5, 2, 4]
+   * });
+   *
+   * @example
+   *
+   * // object with key
+   * var order = [];
+   * var object = { a: 1, b: 5, c: 3, d: 4, e: 2 };
+   * var iterator = function(num, key, done) {
+   *   setTimeout(function() {
+   *     order.push([num, key]);
+   *     done(null, num % 2);
+   *   }, num * 10);
+   * };
+   * async.rejectLimit(object, 2, iterator, function(err, res) {
+   *   console.log(res); // [4, 2]
+   *   console.log(order); // [[1, 'a'], [3, 'c'], [5, 'b'], [2, 'e'], [4, 'd']]
+   * });
+   *
+   */
+  var rejectLimit = createFilterLimit(false);
+
+  /**
+   * @memberof async
+   * @namespace detect
+   * @param {Array|Object} collection
+   * @param {Function} iterator
+   * @param {Function} callback
+   * @example
+   *
+   * // array
+   * var order = [];
+   * var array = [1, 3, 2];
+   * var iterator = function(num, done) {
+   *   setTimeout(function() {
+   *     order.push(num);
+   *     done(null, num % 2);
+   *   }, num * 10);
+   * };
+   * async.detect(array, iterator, function(err, res) {
+   *   console.log(res); // 1
+   *   console.log(order); // [1]
+   * });
+   *
+   * @example
+   *
+   * // array with index
+   * var order = [];
+   * var array = [1, 3, 2];
+   * var iterator = function(num, index, done) {
+   *   setTimeout(function() {
+   *     order.push([num, index]);
+   *     done(null, num % 2);
+   *   }, num * 10);
+   * };
+   * async.detect(array, iterator, function(err, res) {
+   *   console.log(res); // 1
+   *   console.log(order); // [[1, 0]]
+   * });
+   *
+   * @example
+   *
+   * // object
+   * var order = [];
+   * var object = { a: 1, b: 3, c: 2 };
+   * var iterator = function(num, done) {
+   *   setTimeout(function() {
+   *     order.push(num);
+   *     done(null, num % 2);
+   *   }, num * 10);
+   * };
+   * async.detect(object, iterator, function(err, res) {
+   *   console.log(res); // 1
+   *   console.log(order); // [1]
+   * });
+   *
+   * @example
+   *
+   * // object with key
+   * var order = [];
+   * var object = { a: 1, b: 3, c: 2 };
+   * var iterator = function(num, key, done) {
+   *   setTimeout(function() {
+   *     order.push([num, key]);
+   *     done(null, num % 2);
+   *   }, num * 10);
+   * };
+   * async.detect(object, iterator, function(err, res) {
+   *   console.log(res); // 1
+   *   console.log(order); // [[1, 'a']]
+   * });
+   *
+   */
+  var detect = createDetect(arrayEachValue, baseEachValue, symbolEachValue, true);
+
+  /**
+   * @memberof async
+   * @namespace detectSeries
+   * @param {Array|Object} collection
+   * @param {Function} iterator
+   * @param {Function} callback
+   * @example
+   *
+   * // array
+   * var order = [];
+   * var array = [1, 3, 2];
+   * var iterator = function(num, done) {
+   *   setTimeout(function() {
+   *     order.push(num);
+   *     done(null, num % 2);
+   *   }, num * 10);
+   * };
+   * async.detectSeries(array, iterator, function(err, res) {
+   *   console.log(res); // 1
+   *   console.log(order); // [1]
+   * });
+   *
+   * @example
+   *
+   * // array with index
+   * var order = [];
+   * var array = [1, 3, 2];
+   * var iterator = function(num, index, done) {
+   *   setTimeout(function() {
+   *     order.push([num, index]);
+   *     done(null, num % 2);
+   *   }, num * 10);
+   * };
+   * async.detectSeries(array, iterator, function(err, res) {
+   *   console.log(res); // 1
+   *   console.log(order); // [[1, 0]]
+   * });
+   *
+   * @example
+   *
+   * // object
+   * var order = [];
+   * var object = { a: 1, b: 3, c: 2 };
+   * var iterator = function(num, done) {
+   *   setTimeout(function() {
+   *     order.push(num);
+   *     done(null, num % 2);
+   *   }, num * 10);
+   * };
+   * async.detectSeries(object, iterator, function(err, res) {
+   *   console.log(res); // 1
+   *   console.log(order); // [1]
+   * });
+   *
+   * @example
+   *
+   * // object with key
+   * var order = [];
+   * var object = { a: 1, b: 3, c: 2 };
+   * var iterator = function(num, key, done) {
+   *   setTimeout(function() {
+   *     order.push([num, key]);
+   *     done(null, num % 2);
+   *   }, num * 10);
+   * };
+   * async.detectSeries(object, iterator, function(err, res) {
+   *   console.log(res); // 1
+   *   console.log(order); // [[1, 'a']]
+   * });
+   *
+   */
+  var detectSeries = createDetectSeries(true);
+
+  /**
+   * @memberof async
+   * @namespace detectLimit
+   * @param {Array|Object} collection
+   * @param {number} limit - limit >= 1
+   * @param {Function} iterator
+   * @param {Function} callback
+   * @example
+   *
+   * // array
+   * var order = [];
+   * var array = [1, 5, 3, 4, 2];
+   * var iterator = function(num, done) {
+   *   setTimeout(function() {
+   *     order.push(num);
+   *     done(null, num % 2);
+   *   }, num * 10);
+   * };
+   * async.detectLimit(array, 2, iterator, function(err, res) {
+   *   console.log(res); // 1
+   *   console.log(order); // [1]
+   * });
+   *
+   * @example
+   *
+   * // array with index
+   * var order = [];
+   * var array = [1, 5, 3, 4, 2];
+   * var iterator = function(num, index, done) {
+   *   setTimeout(function() {
+   *     order.push([num, index]);
+   *     done(null, num % 2);
+   *   }, num * 10);
+   * };
+   * async.detectLimit(array, 2, iterator, function(err, res) {
+   *   console.log(res); // 1
+   *   console.log(order); // [[1, 0]]
+   * });
+   *
+   * @example
+   *
+   * // object
+   * var order = [];
+   * var object = { a: 1, b: 5, c: 3, d: 4, e: 2 };
+   * var iterator = function(num, done) {
+   *   setTimeout(function() {
+   *     order.push(num);
+   *     done(null, num % 2);
+   *   }, num * 10);
+   * };
+   * async.detectLimit(object, 2, iterator, function(err, res) {
+   *   console.log(res); // 1
+   *   console.log(order); // [1]
+   * });
+   *
+   * @example
+   *
+   * // object with key
+   * var order = [];
+   * var object = { a: 1, b: 5, c: 3, d: 4, e: 2 };
+   * var iterator = function(num, key, done) {
+   *   setTimeout(function() {
+   *     order.push([num, key]);
+   *     done(null, num % 2);
+   *   }, num * 10);
+   * };
+   * async.detectLimit(object, 2, iterator, function(err, res) {
+   *   console.log(res); // 1
+   *   console.log(order); // [[1, 'a']]
+   * });
+   *
+   */
+  var detectLimit = createDetectLimit(true);
+
+  /**
+   * @memberof async
+   * @namespace every
+   * @param {Array|Object} collection
+   * @param {Function} iterator
+   * @param {Function} callback
+   * @example
+   *
+   * // array
+   * var order = [];
+   * var array = [1, 3, 2];
+   * var iterator = function(num, done) {
+   *   setTimeout(function() {
+   *     order.push(num);
+   *     done(null, num % 2);
+   *   }, num * 10);
+   * };
+   * async.every(array, iterator, function(err, res) {
+   *   console.log(res); // false
+   *   console.log(order); // [1, 2]
+   * });
+   *
+   * @example
+   *
+   * // array with index
+   * var order = [];
+   * var array = [1, 3, 2];
+   * var iterator = function(num, index, done) {
+   *   setTimeout(function() {
+   *     order.push([num, index]);
+   *     done(null, num % 2);
+   *   }, num * 10);
+   * };
+   * async.every(array, iterator, function(err, res) {
+   *   console.log(res); // false
+   *   console.log(order); // [[1, 0], [2, 2]]
+   * });
+   *
+   * @example
+   *
+   * // object
+   * var order = [];
+   * var object = { a: 1, b: 3, c: 2 };
+   * var iterator = function(num, done) {
+   *   setTimeout(function() {
+   *     order.push(num);
+   *     done(null, num % 2);
+   *   }, num * 10);
+   * };
+   * async.every(object, iterator, function(err, res) {
+   *   console.log(res); // false
+   *   console.log(order); // [1, 2]
+   * });
+   *
+   * @example
+   *
+   * // object with key
+   * var order = [];
+   * var object = { a: 1, b: 3, c: 2 };
+   * var iterator = function(num, key, done) {
+   *   setTimeout(function() {
+   *     order.push([num, key]);
+   *     done(null, num % 2);
+   *   }, num * 10);
+   * };
+   * async.every(object, iterator, function(err, res) {
+   *   console.log(res); // false
+   *   console.log(order); // [[1, 'a'], [2, 'c']]
+   * });
+   *
+   */
+  var every = createEvery(arrayEachValue, baseEachValue, symbolEachValue);
+
+  /**
+   * @memberof async
+   * @namespace everySeries
+   * @param {Array|Object} collection
+   * @param {Function} iterator
+   * @param {Function} callback
+   * @example
+   *
+   * // array
+   * var order = [];
+   * var array = [1, 3, 2];
+   * var iterator = function(num, done) {
+   *   setTimeout(function() {
+   *     order.push(num);
+   *     done(null, num % 2);
+   *   }, num * 10);
+   * };
+   * async.everySeries(array, iterator, function(err, res) {
+   *   console.log(res); // false
+   *   console.log(order); // [1, 3, 2]
+   * });
+   *
+   * @example
+   *
+   * // array with index
+   * var order = [];
+   * var array = [1, 3, 2];
+   * var iterator = function(num, index, done) {
+   *   setTimeout(function() {
+   *     order.push([num, index]);
+   *     done(null, num % 2);
+   *   }, num * 10);
+   * };
+   * async.everySeries(array, iterator, function(err, res) {
+   *   console.log(res); // false
+   *   console.log(order); // [[1, 0], [3, 1], [2, 2]]
+   * });
+   *
+   * @example
+   *
+   * // object
+   * var order = [];
+   * var object = { a: 1, b: 3, c: 2 };
+   * var iterator = function(num, done) {
+   *   setTimeout(function() {
+   *     order.push(num);
+   *     done(null, num % 2);
+   *   }, num * 10);
+   * };
+   * async.everySeries(object, iterator, function(err, res) {
+   *   console.log(res); // false
+   *   console.log(order); // [1, 3, 2]
+   * });
+   *
+   * @example
+   *
+   * // object with key
+   * var order = [];
+   * var object = { a: 1, b: 3, c: 2 };
+   * var iterator = function(num, key, done) {
+   *   setTimeout(function() {
+   *     order.push([num, key]);
+   *     done(null, num % 2);
+   *   }, num * 10);
+   * };
+   * async.everySeries(object, iterator, function(err, res) {
+   *   console.log(res); // false
+   *   console.log(order); // [[1, 'a'], [3, 'b'] [2, 'c']]
+   * });
+   *
+   */
+  var everySeries = createEverySeries();
+
+  /**
+   * @memberof async
+   * @namespace everyLimit
+   * @param {Array|Object} collection
+   * @param {number} limit - limit >= 1
+   * @param {Function} iterator
+   * @param {Function} callback
+   * @example
+   *
+   * // array
+   * var order = [];
+   * var array = [1, 5, 3, 4, 2];
+   * var iterator = function(num, done) {
+   *   setTimeout(function() {
+   *     order.push(num);
+   *     done(null, num % 2);
+   *   }, num * 10);
+   * };
+   * async.everyLimit(array, 2, iterator, function(err, res) {
+   *   console.log(res); // false
+   *   console.log(order); // [1, 3, 5, 2]
+   * });
+   *
+   * @example
+   *
+   * // array with index
+   * var order = [];
+   * var array = [1, 5, 3, 4, 2];
+   * var iterator = function(num, index, done) {
+   *   setTimeout(function() {
+   *     order.push([num, index]);
+   *     done(null, num % 2);
+   *   }, num * 10);
+   * };
+   * async.everyLimit(array, 2, iterator, function(err, res) {
+   *   console.log(res); // false
+   *   console.log(order); // [[1, 0], [3, 2], [5, 1], [2, 4]]
+   * });
+   *
+   * @example
+   *
+   * // object
+   * var order = [];
+   * var object = { a: 1, b: 5, c: 3, d: 4, e: 2 };
+   * var iterator = function(num, done) {
+   *   setTimeout(function() {
+   *     order.push(num);
+   *     done(null, num % 2);
+   *   }, num * 10);
+   * };
+   * async.everyLimit(object, 2, iterator, function(err, res) {
+   *   console.log(res); // false
+   *   console.log(order); // [1, 3, 5, 2]
+   * });
+   *
+   * @example
+   *
+   * // object with key
+   * var order = [];
+   * var object = { a: 1, b: 5, c: 3, d: 4, e: 2 };
+   * var iterator = function(num, key, done) {
+   *   setTimeout(function() {
+   *     order.push([num, key]);
+   *     done(null, num % 2);
+   *   }, num * 10);
+   * };
+   * async.everyLimit(object, 2, iterator, function(err, res) {
+   *   console.log(res); // false
+   *   console.log(order); // [[1, 'a'], [3, 'c'], [5, 'b'], [2, 'e']]
+   * });
+   *
+   */
+  var everyLimit = createEveryLimit();
+
+  /**
+   * @memberof async
+   * @namespace pick
+   * @param {Array|Object} collection
+   * @param {Function} iterator
+   * @param {Function} callback
+   * @example
+   *
+   * // array
+   * var order = [];
+   * var array = [1, 3, 2, 4];
+   * var iterator = function(num, done) {
+   *   setTimeout(function() {
+   *     order.push(num);
+   *     done(null, num % 2);
+   *   }, num * 10);
+   * };
+   * async.pick(array, iterator, function(err, res) {
+   *   console.log(res); // { '0': 1, '1': 3 }
+   *   console.log(order); // [1, 2, 3, 4]
+   * });
+   *
+   * @example
+   *
+   * // array with index
+   * var order = [];
+   * var array = [1, 3, 2, 4];
+   * var iterator = function(num, index, done) {
+   *   setTimeout(function() {
+   *     order.push([num, index]);
+   *     done(null, num % 2);
+   *   }, num * 10);
+   * };
+   * async.pick(array, iterator, function(err, res) {
+   *   console.log(res); // { '0': 1, '1': 3 }
+   *   console.log(order); // [[0, 1], [2, 2], [3, 1], [4, 3]]
+   * });
+   *
+   * @example
+   *
+   * // object
+   * var order = [];
+   * var object = { a: 1, b: 3, c: 2, d: 4 };
+   * var iterator = function(num, done) {
+   *   setTimeout(function() {
+   *     order.push(num);
+   *     done(null, num % 2);
+   *   }, num * 10);
+   * };
+   * async.pick(object, iterator, function(err, res) {
+   *   console.log(res); // { a: 1, b: 3 }
+   *   console.log(order); // [1, 2, 3, 4]
+   * });
+   *
+   * @example
+   *
+   * // object with key
+   * var order = [];
+   * var object = { a: 1, b: 3, c: 2, d: 4 };
+   * var iterator = function(num, key, done) {
+   *   setTimeout(function() {
+   *     order.push([num, key]);
+   *     done(null, num % 2);
+   *   }, num * 10);
+   * };
+   * async.pick(object, iterator, function(err, res) {
+   *   console.log(res); // { a: 1, b: 3 }
+   *   console.log(order); // [[1, 'a'], [2, 'c'], [3, 'b'], [4, 'd']]
+   * });
+   *
+   */
+  var pick = createPick(arrayEachIndexValue, baseEachKeyValue, symbolEachKeyValue, true);
+
+  /**
+   * @memberof async
+   * @namespace pickSeries
+   * @param {Array|Object} collection
+   * @param {Function} iterator
+   * @param {Function} callback
+   * @example
+   *
+   * // array
+   * var order = [];
+   * var array = [1, 3, 2, 4];
+   * var iterator = function(num, done) {
+   *   setTimeout(function() {
+   *     order.push(num);
+   *     done(null, num % 2);
+   *   }, num * 10);
+   * };
+   * async.pickSeries(array, iterator, function(err, res) {
+   *   console.log(res); // { '0': 1, '1': 3 }
+   *   console.log(order); // [1, 3, 2, 4]
+   * });
+   *
+   * @example
+   *
+   * // array with index
+   * var order = [];
+   * var array = [1, 3, 2, 4];
+   * var iterator = function(num, index, done) {
+   *   setTimeout(function() {
+   *     order.push([num, index]);
+   *     done(null, num % 2);
+   *   }, num * 10);
+   * };
+   * async.pickSeries(array, iterator, function(err, res) {
+   *   console.log(res); // { '0': 1, '1': 3 }
+   *   console.log(order); // [[0, 1], [3, 1], [2, 2], [4, 3]]
+   * });
+   *
+   * @example
+   *
+   * // object
+   * var order = [];
+   * var object = { a: 1, b: 3, c: 2, d: 4 };
+   * var iterator = function(num, done) {
+   *   setTimeout(function() {
+   *     order.push(num);
+   *     done(null, num % 2);
+   *   }, num * 10);
+   * };
+   * async.pickSeries(object, iterator, function(err, res) {
+   *   console.log(res); // { a: 1, b: 3 }
+   *   console.log(order); // [1, 3, 2, 4]
+   * });
+   *
+   * @example
+   *
+   * // object with key
+   * var order = [];
+   * var object = { a: 1, b: 3, c: 2, d: 4 };
+   * var iterator = function(num, key, done) {
+   *   setTimeout(function() {
+   *     order.push([num, key]);
+   *     done(null, num % 2);
+   *   }, num * 10);
+   * };
+   * async.pickSeries(object, iterator, function(err, res) {
+   *   console.log(res); // { a: 1, b: 3 }
+   *   console.log(order); // [[1, 'a'], [3, 'b'], [2, 'c'], [4, 'd']]
+   * });
+   *
+   */
+  var pickSeries = createPickSeries(true);
+
+  /**
+   * @memberof async
+   * @namespace pickLimit
+   * @param {Array|Object} collection
+   * @param {number} limit - limit >= 1
+   * @param {Function} iterator
+   * @param {Function} callback
+   * @example
+   *
+   * // array
+   * var order = [];
+   * var array = [1, 5, 3, 4, 2];
+   * var iterator = function(num, done) {
+   *   setTimeout(function() {
+   *     order.push(num);
+   *     done(null, num % 2);
+   *   }, num * 10);
+   * };
+   * async.pickLimit(array, 2, iterator, function(err, res) {
+   *   console.log(res); // { '0': 1, '1': 5, '2': 3 }
+   *   console.log(order); // [1, 3, 5, 2, 4]
+   * });
+   *
+   * @example
+   *
+   * // array with index
+   * var order = [];
+   * var array = [1, 5, 3, 4, 2];
+   * var iterator = function(num, index, done) {
+   *   setTimeout(function() {
+   *     order.push([num, index]);
+   *     done(null, num % 2);
+   *   }, num * 10);
+   * };
+   * async.pickLimit(array, 2, iterator, function(err, res) {
+   *   console.log(res); // { '0': 1, '1': 5, '2': 3 }
+   *   console.log(order); // [[1, 0], [3, 2], [5, 1], [2, 4], [4, 3]]
+   * });
+   *
+   * @example
+   *
+   * // object
+   * var order = [];
+   * var object = { a: 1, b: 5, c: 3, d: 4, e: 2 };
+   * var iterator = function(num, done) {
+   *   setTimeout(function() {
+   *     order.push(num);
+   *     done(null, num % 2);
+   *   }, num * 10);
+   * };
+   * async.pickLimit(object, 2, iterator, function(err, res) {
+   *   console.log(res); // { a: 1, b: 5, c: 3 }
+   *   console.log(order); // [1, 3, 5, 2, 4]
+   * });
+   *
+   * @example
+   *
+   * // object with key
+   * var order = [];
+   * var object = { a: 1, b: 5, c: 3, d: 4, e: 2 };
+   * var iterator = function(num, key, done) {
+   *   setTimeout(function() {
+   *     order.push([num, key]);
+   *     done(null, num % 2);
+   *   }, num * 10);
+   * };
+   * async.pickLimit(object, 2, iterator, function(err, res) {
+   *   console.log(res); // { a: 1, b: 5, c: 3 }
+   *   console.log(order); // [[1, 'a'], [3, 'c'], [5, 'b'], [2, 'e'], [4, 'd']]
+   * });
+   *
+   */
+  var pickLimit = createPickLimit(true);
+
+  /**
+   * @memberof async
+   * @namespace omit
+   * @param {Array|Object} collection
+   * @param {Function} iterator
+   * @param {Function} callback
+   * @example
+   *
+   * // array
+   * var order = [];
+   * var array = [1, 3, 2, 4];
+   * var iterator = function(num, done) {
+   *   setTimeout(function() {
+   *     order.push(num);
+   *     done(null, num % 2);
+   *   }, num * 10);
+   * };
+   * async.omit(array, iterator, function(err, res) {
+   *   console.log(res); // { '2': 2, '3': 4 }
+   *   console.log(order); // [1, 2, 3, 4]
+   * });
+   *
+   * @example
+   *
+   * // array with index
+   * var order = [];
+   * var array = [1, 3, 2, 4];
+   * var iterator = function(num, index, done) {
+   *   setTimeout(function() {
+   *     order.push([num, index]);
+   *     done(null, num % 2);
+   *   }, num * 10);
+   * };
+   * async.omit(array, iterator, function(err, res) {
+   *   console.log(res); // { '2': 2, '3': 4 }
+   *   console.log(order); // [[0, 1], [2, 2], [3, 1], [4, 3]]
+   * });
+   *
+   * @example
+   *
+   * // object
+   * var order = [];
+   * var object = { a: 1, b: 3, c: 2, d: 4 };
+   * var iterator = function(num, done) {
+   *   setTimeout(function() {
+   *     order.push(num);
+   *     done(null, num % 2);
+   *   }, num * 10);
+   * };
+   * async.omit(object, iterator, function(err, res) {
+   *   console.log(res); // { c: 2, d: 4 }
+   *   console.log(order); // [1, 2, 3, 4]
+   * });
+   *
+   * @example
+   *
+   * // object with key
+   * var order = [];
+   * var object = { a: 1, b: 3, c: 2, d: 4 };
+   * var iterator = function(num, key, done) {
+   *   setTimeout(function() {
+   *     order.push([num, key]);
+   *     done(null, num % 2);
+   *   }, num * 10);
+   * };
+   * async.omit(object, iterator, function(err, res) {
+   *   console.log(res); // { c: 2, d: 4 }
+   *   console.log(order); // [[1, 'a'], [2, 'c'], [3, 'b'], [4, 'd']]
+   * });
+   *
+   */
+  var omit = createPick(arrayEachIndexValue, baseEachKeyValue, symbolEachKeyValue, false);
+
+  /**
+   * @memberof async
+   * @namespace omitSeries
+   * @param {Array|Object} collection
+   * @param {Function} iterator
+   * @param {Function} callback
+   * @example
+   *
+   * // array
+   * var order = [];
+   * var array = [1, 3, 2, 4];
+   * var iterator = function(num, done) {
+   *   setTimeout(function() {
+   *     order.push(num);
+   *     done(null, num % 2);
+   *   }, num * 10);
+   * };
+   * async.omitSeries(array, iterator, function(err, res) {
+   *   console.log(res); // { '2': 2, '3': 4 }
+   *   console.log(order); // [1, 3, 2, 4]
+   * });
+   *
+   * @example
+   *
+   * // array with index
+   * var order = [];
+   * var array = [1, 3, 2, 4];
+   * var iterator = function(num, index, done) {
+   *   setTimeout(function() {
+   *     order.push([num, index]);
+   *     done(null, num % 2);
+   *   }, num * 10);
+   * };
+   * async.omitSeries(array, iterator, function(err, res) {
+   *   console.log(res); // { '2': 2, '3': 4 }
+   *   console.log(order); // [[0, 1], [3, 1], [2, 2], [4, 3]]
+   * });
+   *
+   * @example
+   *
+   * // object
+   * var order = [];
+   * var object = { a: 1, b: 3, c: 2, d: 4 };
+   * var iterator = function(num, done) {
+   *   setTimeout(function() {
+   *     order.push(num);
+   *     done(null, num % 2);
+   *   }, num * 10);
+   * };
+   * async.omitSeries(object, iterator, function(err, res) {
+   *   console.log(res); // { c: 2, d: 4 }
+   *   console.log(order); // [1, 3, 2, 4]
+   * });
+   *
+   * @example
+   *
+   * // object with key
+   * var order = [];
+   * var object = { a: 1, b: 3, c: 2, d: 4 };
+   * var iterator = function(num, key, done) {
+   *   setTimeout(function() {
+   *     order.push([num, key]);
+   *     done(null, num % 2);
+   *   }, num * 10);
+   * };
+   * async.omitSeries(object, iterator, function(err, res) {
+   *   console.log(res); // { c: 2, d: 4 }
+   *   console.log(order); // [[1, 'a'], [3, 'b'], [2, 'c'], [4, 'd']]
+   * });
+   *
+   */
+  var omitSeries = createPickSeries(false);
+
+  /**
+   * @memberof async
+   * @namespace omitLimit
+   * @param {Array|Object} collection
+   * @param {number} limit - limit >= 1
+   * @param {Function} iterator
+   * @param {Function} callback
+   * @example
+   *
+   * // array
+   * var order = [];
+   * var array = [1, 5, 3, 4, 2];
+   * var iterator = function(num, done) {
+   *   setTimeout(function() {
+   *     order.push(num);
+   *     done(null, num % 2);
+   *   }, num * 10);
+   * };
+   * async.omitLimit(array, 2, iterator, function(err, res) {
+   *   console.log(res); // { '3': 4, '4': 2 }
+   *   console.log(order); // [1, 3, 5, 2, 4]
+   * });
+   *
+   * @example
+   *
+   * // array with index
+   * var order = [];
+   * var array = [1, 5, 3, 4, 2];
+   * var iterator = function(num, index, done) {
+   *   setTimeout(function() {
+   *     order.push([num, index]);
+   *     done(null, num % 2);
+   *   }, num * 10);
+   * };
+   * async.omitLimit(array, 2, iterator, function(err, res) {
+   *   console.log(res); // { '3': 4, '4': 2 }
+   *   console.log(order); // [[1, 0], [3, 2], [5, 1], [2, 4], [4, 3]]
+   * });
+   *
+   * @example
+   *
+   * // object
+   * var order = [];
+   * var object = { a: 1, b: 5, c: 3, d: 4, e: 2 };
+   * var iterator = function(num, done) {
+   *   setTimeout(function() {
+   *     order.push(num);
+   *     done(null, num % 2);
+   *   }, num * 10);
+   * };
+   * async.omitLimit(object, 2, iterator, function(err, res) {
+   *   console.log(res); // { d: 4, e: 2 }
+   *   console.log(order); // [1, 3, 5, 2, 4]
+   * });
+   *
+   * @example
+   *
+   * // object with key
+   * var order = [];
+   * var object = { a: 1, b: 5, c: 3, d: 4, e: 2 };
+   * var iterator = function(num, key, done) {
+   *   setTimeout(function() {
+   *     order.push([num, key]);
+   *     done(null, num % 2);
+   *   }, num * 10);
+   * };
+   * async.omitLimit(object, 2, iterator, function(err, res) {
+   *   console.log(res); // { d: 4, e: 2 }
+   *   console.log(order); // [[1, 'a'], [3, 'c'], [5, 'b'], [2, 'e'], [4, 'd']]
+   * });
+   *
+   */
+  var omitLimit = createPickLimit(false);
+
+  /**
+   * @memberof async
+   * @namespace transform
+   * @param {Array|Object} collection
+   * @param {Array|Object|Function} [accumulator]
+   * @param {Function} [iterator]
+   * @param {Function} [callback]
+   * @example
+   *
+   * // array
+   * var order = [];
+   * var collection = [1, 3, 2, 4];
+   * var iterator = function(result, num, done) {
+   *   setTimeout(function() {
+   *     order.push(num);
+   *     result.push(num)
+   *     done();
+   *   }, num * 10);
+   * };
+   * async.transform(collection, iterator, function(err, res) {
+   *   console.log(res); // [1, 2, 3, 4]
+   *   console.log(order); // [1, 2, 3, 4]
+   * });
+   *
+   * @example
+   *
+   * // array with index and accumulator
+   * var order = [];
+   * var collection = [1, 3, 2, 4];
+   * var iterator = function(result, num, index, done) {
+   *   setTimeout(function() {
+   *     order.push([num, index]);
+   *     result[index] = num;
+   *     done();
+   *   }, num * 10);
+   * };
+   * async.transform(collection, {}, iterator, function(err, res) {
+   *   console.log(res); // { '0': 1, '1': 3, '2': 2, '3': 4 }
+   *   console.log(order); // [[1, 0], [2, 2], [3, 1], [4, 3]]
+   * });
+   *
+   * @example
+   *
+   * // object with accumulator
+   * var order = [];
+   * var object = { a: 1, b: 3, c: 2, d: 4 };
+   * var iterator = function(result, num, done) {
+   *   setTimeout(function() {
+   *     order.push(num);
+   *     result.push(num);
+   *     done();
+   *   }, num * 10);
+   * };
+   * async.transform(collection, [], iterator, function(err, res) {
+   *   console.log(res); // [1, 2, 3, 4]
+   *   console.log(order); // [1, 2, 3, 4]
+   * });
+   *
+   * @example
+   *
+   * // object with key
+   * var order = [];
+   * var object = { a: 1, b: 3, c: 2, d: 4 };
+   * var iterator = function(result, num, key, done) {
+   *   setTimeout(function() {
+   *     order.push([num, key]);
+   *     result[key] = num;
+   *     done();
+   *   }, num * 10);
+   * };
+   * async.transform(collection, iterator, function(err, res) {
+   *   console.log(res); //  { a: 1, b: 3, c: 2, d: 4 }
+   *   console.log(order); // [[1, 'a'], [2, 'c'], [3, 'b'], [4, 'd']]
+   * });
+   *
+   */
+  var transform = createTransform(arrayEachResult, baseEachResult, symbolEachResult);
+
+  /**
+   * @memberof async
+   * @namespace sortBy
+   * @param {Array|Object} collection
+   * @param {Function} iterator
+   * @param {Function} callback
+   * @example
+   *
+   * // array
+   * var order = [];
+   * var array = [1, 3, 2];
+   * var iterator = function(num, done) {
+   *   setTimeout(function() {
+   *     order.push(num);
+   *     done(null, num);
+   *   }, num * 10);
+   * };
+   * async.sortBy(array, iterator, function(err, res) {
+   *   console.log(res); // [1, 2, 3];
+   *   console.log(order); // [1, 2, 3]
+   * });
+   *
+   * @example
+   *
+   * // array with index
+   * var order = [];
+   * var array = [1, 3, 2];
+   * var iterator = function(num, index, done) {
+   *   setTimeout(function() {
+   *     order.push([num, index]);
+   *     done(null, num);
+   *   }, num * 10);
+   * };
+   * async.sortBy(array, iterator, function(err, res) {
+   *   console.log(res); // [1, 2, 3]
+   *   console.log(order); // [[1, 0], [2, 2], [3, 1]]
+   * });
+   *
+   * @example
+   *
+   * // object
+   * var order = [];
+   * var object = { a: 1, b: 3, c: 2 };
+   * var iterator = function(num, done) {
+   *   setTimeout(function() {
+   *     order.push(num);
+   *     done(null, num);
+   *   }, num * 10);
+   * };
+   * async.sortBy(object, iterator, function(err, res) {
+   *   console.log(res); // [1, 2, 3]
+   *   console.log(order); // [1, 2, 3]
+   * });
+   *
+   * @example
+   *
+   * // object with key
+   * var order = [];
+   * var object = { a: 1, b: 3, c: 2 };
+   * var iterator = function(num, key, done) {
+   *   setTimeout(function() {
+   *     order.push([num, key]);
+   *     done(null, num);
+   *   }, num * 10);
+   * };
+   * async.sortBy(object, iterator, function(err, res) {
+   *   console.log(res); // [1, 2, 3]
+   *   console.log(order); // [[1, 'a'], [2, 'c'], [3, 'b']]
+   * });
+   *
+   */
+  var sortBy = createSortBy(arrayEachIndexValue, baseEachIndexValue, symbolEachIndexValue);
+
+  /**
+   * @memberof async
+   * @namespace concat
+   * @param {Array|Object} collection
+   * @param {Function} iterator
+   * @param {Function} callback
+   * @example
+   *
+   * // array
+   * var order = [];
+   * var array = [1, 3, 2];
+   * var iterator = function(num, done) {
+   *   setTimeout(function() {
+   *     order.push(num);
+   *     done(null, [num]);
+   *   }, num * 10);
+   * };
+   * async.concat(array, iterator, function(err, res) {
+   *   console.log(res); // [1, 2, 3];
+   *   console.log(order); // [1, 2, 3]
+   * });
+   *
+   * @example
+   *
+   * // array with index
+   * var order = [];
+   * var array = [1, 3, 2];
+   * var iterator = function(num, index, done) {
+   *   setTimeout(function() {
+   *     order.push([num, index]);
+   *     done(null, [num]);
+   *   }, num * 10);
+   * };
+   * async.concat(array, iterator, function(err, res) {
+   *   console.log(res); // [1, 2, 3]
+   *   console.log(order); // [[1, 0], [2, 2], [3, 1]]
+   * });
+   *
+   * @example
+   *
+   * // object
+   * var order = [];
+   * var object = { a: 1, b: 3, c: 2 };
+   * var iterator = function(num, done) {
+   *   setTimeout(function() {
+   *     order.push(num);
+   *     done(null, [num]);
+   *   }, num * 10);
+   * };
+   * async.concat(object, iterator, function(err, res) {
+   *   console.log(res); // [1, 2, 3]
+   *   console.log(order); // [1, 2, 3]
+   * });
+   *
+   * @example
+   *
+   * // object with key
+   * var order = [];
+   * var object = { a: 1, b: 3, c: 2 };
+   * var iterator = function(num, key, done) {
+   *   setTimeout(function() {
+   *     order.push([num, key]);
+   *     done(null, [num]);
+   *   }, num * 10);
+   * };
+   * async.concat(object, iterator, function(err, res) {
+   *   console.log(res); // [1, 2, 3]
+   *   console.log(order); // [[1, 'a'], [2, 'c'], [3, 'b']]
+   * });
+   *
+   */
+  var concat = createConcat(arrayEachIndex, baseEachIndex, symbolEachIndex);
+
+  /**
+   * @memberof async
+   * @namespace groupBy
+   * @param {Array|Object} collection
+   * @param {Function} iterator
+   * @param {Function} callback
+   * @example
+   *
+   * // array
+   * var order = [];
+   * var array = [4.2, 6.4, 6.1];
+   * var iterator = function(num, done) {
+   *   setTimeout(function() {
+   *     order.push(num);
+   *     done(null, Math.floor(num));
+   *   }, num * 10);
+   * };
+   * async.groupBy(array, iterator, function(err, res) {
+   *   console.log(res); // { '4': [4.2], '6': [6.1, 6.4] }
+   *   console.log(order); // [4.2, 6.1, 6.4]
+   * });
+   *
+   * @example
+   *
+   * // array with index
+   * var order = [];
+   * var array = [4.2, 6.4, 6.1];
+   * var iterator = function(num, index, done) {
+   *   setTimeout(function() {
+   *     order.push([num, index]);
+   *     done(null, Math.floor(num));
+   *   }, num * 10);
+   * };
+   * async.groupBy(array, iterator, function(err, res) {
+   *   console.log(res); // { '4': [4.2], '6': [6.1, 6.4] }
+   *   console.log(order); // [[4.2, 0], [6.1, 2], [6.4, 1]]
+   * });
+   *
+   * @example
+   *
+   * // object
+   * var order = [];
+   * var object = { a: 4.2, b: 6.4, c: 6.1 };
+   * var iterator = function(num, done) {
+   *   setTimeout(function() {
+   *     order.push(num);
+   *     done(null, Math.floor(num));
+   *   }, num * 10);
+   * };
+   * async.groupBy(object, iterator, function(err, res) {
+   *   console.log(res); // { '4': [4.2], '6': [6.1, 6.4] }
+   *   console.log(order); // [4.2, 6.1, 6.4]
+   * });
+   *
+   * @example
+   *
+   * // object with key
+   * var order = [];
+   * var object = { a: 4.2, b: 6.4, c: 6.1 };
+   * var iterator = function(num, key, done) {
+   *   setTimeout(function() {
+   *     order.push([num, key]);
+   *     done(null, Math.floor(num));
+   *   }, num * 10);
+   * };
+   * async.groupBy(object, iterator, function(err, res) {
+   *   console.log(res); // { '4': [4.2], '6': [6.1, 6.4] }
+   *   console.log(order); // [[4.2, 'a'], [6.1, 'c'], [6.4, 'b']]
+   * });
+   *
+   */
+  var groupBy = createGroupBy(arrayEachValue, baseEachValue, symbolEachValue);
+
+  /**
+   * @memberof async
+   * @namespace parallel
+   * @param {Array|Object} tasks - functions
+   * @param {Function} callback
+   * @example
+   *
+   * var order = [];
+   * var tasks = [
+   *  function(done) {
+   *    setTimeout(function() {
+   *      order.push(1);
+   *      done(null, 1);
+   *    }, 10);
+   *  },
+   *  function(done) {
+   *    setTimeout(function() {
+   *      order.push(2);
+   *      done(null, 2);
+   *    }, 30);
+   *  },
+   *  function(done) {
+   *    setTimeout(function() {
+   *      order.push(3);
+   *      done(null, 3);
+   *    }, 40);
+   *  },
+   *  function(done) {
+   *    setTimeout(function() {
+   *      order.push(4);
+   *      done(null, 4);
+   *    }, 20);
+   *  }
+   * ];
+   * async.parallel(tasks, function(err, res) {
+   *   console.log(res); // [1, 2, 3, 4];
+   *   console.log(order); // [1, 4, 2, 3]
+   * });
+   *
+   * @example
+   *
+   * var order = [];
+   * var tasks = {
+   *   'a': function(done) {
+   *     setTimeout(function() {
+   *       order.push(1);
+   *       done(null, 1);
+   *     }, 10);
+   *   },
+   *   'b': function(done) {
+   *     setTimeout(function() {
+   *       order.push(2);
+   *       done(null, 2);
+   *     }, 30);
+   *   },
+   *   'c': function(done) {
+   *     setTimeout(function() {
+   *       order.push(3);
+   *       done(null, 3);
+   *     }, 40);
+   *   },
+   *   'd': function(done) {
+   *     setTimeout(function() {
+   *       order.push(4);
+   *       done(null, 4);
+   *     }, 20);
+   *   }
+   * };
+   * async.parallel(tasks, function(err, res) {
+   *   console.log(res); // { a: 1, b: 2, c: 3, d:4 }
+   *   console.log(order); // [1, 4, 2, 3]
+   * });
+   *
+   */
+  var parallel = createParallel(arrayEachFunc, baseEachFunc);
+
+  /**
+   * @memberof async
+   * @namespace applyEach
+   */
+  var applyEach = createApplyEach(map);
+
+  /**
+   * @memberof async
+   * @namespace applyEachSeries
+   */
+  var applyEachSeries = createApplyEach(mapSeries);
+
+  /**
+   * @memberof async
+   * @namespace log
+   */
+  var log = createLogger('log');
+
+  /**
+   * @memberof async
+   * @namespace dir
+   */
+  var dir = createLogger('dir');
+
+  /**
+   * @version 2.6.2
+   * @namespace async
+   */
+  var index = {
+    VERSION: '2.6.2',
+
+    // Collections
+    each: each,
+    eachSeries: eachSeries,
+    eachLimit: eachLimit,
+    forEach: each,
+    forEachSeries: eachSeries,
+    forEachLimit: eachLimit,
+    eachOf: each,
+    eachOfSeries: eachSeries,
+    eachOfLimit: eachLimit,
+    forEachOf: each,
+    forEachOfSeries: eachSeries,
+    forEachOfLimit: eachLimit,
+    map: map,
+    mapSeries: mapSeries,
+    mapLimit: mapLimit,
+    mapValues: mapValues,
+    mapValuesSeries: mapValuesSeries,
+    mapValuesLimit: mapValuesLimit,
+    filter: filter,
+    filterSeries: filterSeries,
+    filterLimit: filterLimit,
+    select: filter,
+    selectSeries: filterSeries,
+    selectLimit: filterLimit,
+    reject: reject,
+    rejectSeries: rejectSeries,
+    rejectLimit: rejectLimit,
+    detect: detect,
+    detectSeries: detectSeries,
+    detectLimit: detectLimit,
+    find: detect,
+    findSeries: detectSeries,
+    findLimit: detectLimit,
+    pick: pick,
+    pickSeries: pickSeries,
+    pickLimit: pickLimit,
+    omit: omit,
+    omitSeries: omitSeries,
+    omitLimit: omitLimit,
+    reduce: reduce,
+    inject: reduce,
+    foldl: reduce,
+    reduceRight: reduceRight,
+    foldr: reduceRight,
+    transform: transform,
+    transformSeries: transformSeries,
+    transformLimit: transformLimit,
+    sortBy: sortBy,
+    sortBySeries: sortBySeries,
+    sortByLimit: sortByLimit,
+    some: some,
+    someSeries: someSeries,
+    someLimit: someLimit,
+    any: some,
+    anySeries: someSeries,
+    anyLimit: someLimit,
+    every: every,
+    everySeries: everySeries,
+    everyLimit: everyLimit,
+    all: every,
+    allSeries: everySeries,
+    allLimit: everyLimit,
+    concat: concat,
+    concatSeries: concatSeries,
+    concatLimit: concatLimit,
+    groupBy: groupBy,
+    groupBySeries: groupBySeries,
+    groupByLimit: groupByLimit,
+
+    // Control Flow
+    parallel: parallel,
+    series: series,
+    parallelLimit: parallelLimit,
+    tryEach: tryEach,
+    waterfall: waterfall,
+    angelFall: angelFall,
+    angelfall: angelFall,
+    whilst: whilst,
+    doWhilst: doWhilst,
+    until: until,
+    doUntil: doUntil,
+    during: during,
+    doDuring: doDuring,
+    forever: forever,
+    compose: compose,
+    seq: seq,
+    applyEach: applyEach,
+    applyEachSeries: applyEachSeries,
+    queue: queue,
+    priorityQueue: priorityQueue,
+    cargo: cargo,
+    auto: auto,
+    autoInject: autoInject,
+    retry: retry,
+    retryable: retryable,
+    iterator: iterator,
+    times: times,
+    timesSeries: timesSeries,
+    timesLimit: timesLimit,
+    race: race,
+
+    // Utils
+    apply: apply,
+    nextTick: asyncNextTick,
+    setImmediate: asyncSetImmediate,
+    memoize: memoize,
+    unmemoize: unmemoize,
+    ensureAsync: ensureAsync,
+    constant: constant,
+    asyncify: asyncify,
+    wrapSync: asyncify,
+    log: log,
+    dir: dir,
+    reflect: reflect,
+    reflectAll: reflectAll,
+    timeout: timeout,
+    createLogger: createLogger,
+
+    // Mode
+    safe: safe,
+    fast: fast
+  };
+
+  exports['default'] = index;
+  baseEachSync(
+    index,
+    function(func, key) {
+      exports[key] = func;
+    },
+    nativeKeys(index)
+  );
+
+  /**
+   * @private
+   */
+  function createImmediate(safeMode) {
+    var delay = function delay(fn) {
+      var args = slice(arguments, 1);
+      setTimeout(function() {
+        fn.apply(null, args);
+      });
+    };
+    asyncSetImmediate = typeof setImmediate === func ? setImmediate : delay;
+    if (typeof process === obj && typeof process.nextTick === func) {
+      nextTick = /^v0.10/.test(process.version) ? asyncSetImmediate : process.nextTick;
+      asyncNextTick = /^v0/.test(process.version) ? asyncSetImmediate : process.nextTick;
+    } else {
+      asyncNextTick = nextTick = asyncSetImmediate;
+    }
+    if (safeMode === false) {
+      nextTick = function(cb) {
+        cb();
+      };
+    }
+  }
+
+  /* sync functions based on lodash */
+
+  /**
+   * Converts `arguments` to an array.
+   *
+   * @private
+   * @param {Array} array = The array to slice.
+   */
+  function createArray(array) {
+    var index = -1;
+    var size = array.length;
+    var result = Array(size);
+
+    while (++index < size) {
+      result[index] = array[index];
+    }
+    return result;
+  }
+
+  /**
+   * Create an array from `start`
+   *
+   * @private
+   * @param {Array} array - The array to slice.
+   * @param {number} start - The start position.
+   */
+  function slice(array, start) {
+    var end = array.length;
+    var index = -1;
+    var size = end - start;
+    if (size <= 0) {
+      return [];
+    }
+    var result = Array(size);
+
+    while (++index < size) {
+      result[index] = array[index + start];
+    }
+    return result;
+  }
+
+  /**
+   * @private
+   * @param {Object} object
+   */
+  function objectClone(object) {
+    var keys = nativeKeys(object);
+    var size = keys.length;
+    var index = -1;
+    var result = {};
+
+    while (++index < size) {
+      var key = keys[index];
+      result[key] = object[key];
+    }
+    return result;
+  }
+
+  /**
+   * Create an array with all falsey values removed.
+   *
+   * @private
+   * @param {Array} array - The array to compact.
+   */
+  function compact(array) {
+    var index = -1;
+    var size = array.length;
+    var result = [];
+
+    while (++index < size) {
+      var value = array[index];
+      if (value) {
+        result[result.length] = value;
+      }
+    }
+    return result;
+  }
+
+  /**
+   * Create an array of reverse sequence.
+   *
+   * @private
+   * @param {Array} array - The array to reverse.
+   */
+  function reverse(array) {
+    var index = -1;
+    var size = array.length;
+    var result = Array(size);
+    var resIndex = size;
+
+    while (++index < size) {
+      result[--resIndex] = array[index];
+    }
+    return result;
+  }
+
+  /**
+   * Checks if key exists in object property.
+   *
+   * @private
+   * @param {Object} object - The object to inspect.
+   * @param {string} key - The key to check.
+   */
+  function has(object, key) {
+    return object.hasOwnProperty(key);
+  }
+
+  /**
+   * Check if target exists in array.
+   * @private
+   * @param {Array} array
+   * @param {*} target
+   */
+  function notInclude(array, target) {
+    var index = -1;
+    var size = array.length;
+
+    while (++index < size) {
+      if (array[index] === target) {
+        return false;
+      }
+    }
+    return true;
+  }
+
+  /**
+   * @private
+   * @param {Array} array - The array to iterate over.
+   * @param {Function} iterator - The function invoked per iteration.
+   */
+  function arrayEachSync(array, iterator) {
+    var index = -1;
+    var size = array.length;
+
+    while (++index < size) {
+      iterator(array[index], index);
+    }
+    return array;
+  }
+
+  /**
+   * @private
+   * @param {Object} object - The object to iterate over.
+   * @param {Function} iterator - The function invoked per iteration.
+   * @param {Array} keys
+   */
+  function baseEachSync(object, iterator, keys) {
+    var index = -1;
+    var size = keys.length;
+
+    while (++index < size) {
+      var key = keys[index];
+      iterator(object[key], key);
+    }
+    return object;
+  }
+
+  /**
+   * @private
+   * @param {number} n
+   * @param {Function} iterator
+   */
+  function timesSync(n, iterator) {
+    var index = -1;
+    while (++index < n) {
+      iterator(index);
+    }
+  }
+
+  /**
+   * @private
+   * @param {Array} array
+   * @param {number[]} criteria
+   */
+  function sortByCriteria(array, criteria) {
+    var l = array.length;
+    var indices = Array(l);
+    var i;
+    for (i = 0; i < l; i++) {
+      indices[i] = i;
+    }
+    quickSort(criteria, 0, l - 1, indices);
+    var result = Array(l);
+    for (var n = 0; n < l; n++) {
+      i = indices[n];
+      result[n] = i === undefined ? array[n] : array[i];
+    }
+    return result;
+  }
+
+  function partition(array, i, j, mid, indices) {
+    var l = i;
+    var r = j;
+    while (l <= r) {
+      i = l;
+      while (l < r && array[l] < mid) {
+        l++;
+      }
+      while (r >= i && array[r] >= mid) {
+        r--;
+      }
+      if (l > r) {
+        break;
+      }
+      swap(array, indices, l++, r--);
+    }
+    return l;
+  }
+
+  function swap(array, indices, l, r) {
+    var n = array[l];
+    array[l] = array[r];
+    array[r] = n;
+    var i = indices[l];
+    indices[l] = indices[r];
+    indices[r] = i;
+  }
+
+  function quickSort(array, i, j, indices) {
+    if (i === j) {
+      return;
+    }
+    var k = i;
+    while (++k <= j && array[i] === array[k]) {
+      var l = k - 1;
+      if (indices[l] > indices[k]) {
+        var index = indices[l];
+        indices[l] = indices[k];
+        indices[k] = index;
+      }
+    }
+    if (k > j) {
+      return;
+    }
+    var p = array[i] > array[k] ? i : k;
+    k = partition(array, i, j, array[p], indices);
+    quickSort(array, i, k - 1, indices);
+    quickSort(array, k, j, indices);
+  }
+
+  /**
+   * @Private
+   */
+  function makeConcatResult(array) {
+    var result = [];
+    arrayEachSync(array, function(value) {
+      if (value === noop) {
+        return;
+      }
+      if (isArray(value)) {
+        nativePush.apply(result, value);
+      } else {
+        result.push(value);
+      }
+    });
+    return result;
+  }
+
+  /* async functions */
+
+  /**
+   * @private
+   */
+  function arrayEach(array, iterator, callback) {
+    var index = -1;
+    var size = array.length;
+
+    if (iterator.length === 3) {
+      while (++index < size) {
+        iterator(array[index], index, onlyOnce(callback));
+      }
+    } else {
+      while (++index < size) {
+        iterator(array[index], onlyOnce(callback));
+      }
+    }
+  }
+
+  /**
+   * @private
+   */
+  function baseEach(object, iterator, callback, keys) {
+    var key;
+    var index = -1;
+    var size = keys.length;
+
+    if (iterator.length === 3) {
+      while (++index < size) {
+        key = keys[index];
+        iterator(object[key], key, onlyOnce(callback));
+      }
+    } else {
+      while (++index < size) {
+        iterator(object[keys[index]], onlyOnce(callback));
+      }
+    }
+  }
+
+  /**
+   * @private
+   */
+  function symbolEach(collection, iterator, callback) {
+    var iter = collection[iteratorSymbol]();
+    var index = 0;
+    var item;
+    if (iterator.length === 3) {
+      while ((item = iter.next()).done === false) {
+        iterator(item.value, index++, onlyOnce(callback));
+      }
+    } else {
+      while ((item = iter.next()).done === false) {
+        index++;
+        iterator(item.value, onlyOnce(callback));
+      }
+    }
+    return index;
+  }
+
+  /**
+   * @private
+   */
+  function arrayEachResult(array, result, iterator, callback) {
+    var index = -1;
+    var size = array.length;
+
+    if (iterator.length === 4) {
+      while (++index < size) {
+        iterator(result, array[index], index, onlyOnce(callback));
+      }
+    } else {
+      while (++index < size) {
+        iterator(result, array[index], onlyOnce(callback));
+      }
+    }
+  }
+
+  /**
+   * @private
+   */
+  function baseEachResult(object, result, iterator, callback, keys) {
+    var key;
+    var index = -1;
+    var size = keys.length;
+
+    if (iterator.length === 4) {
+      while (++index < size) {
+        key = keys[index];
+        iterator(result, object[key], key, onlyOnce(callback));
+      }
+    } else {
+      while (++index < size) {
+        iterator(result, object[keys[index]], onlyOnce(callback));
+      }
+    }
+  }
+
+  /**
+   * @private
+   */
+  function symbolEachResult(collection, result, iterator, callback) {
+    var item;
+    var index = 0;
+    var iter = collection[iteratorSymbol]();
+
+    if (iterator.length === 4) {
+      while ((item = iter.next()).done === false) {
+        iterator(result, item.value, index++, onlyOnce(callback));
+      }
+    } else {
+      while ((item = iter.next()).done === false) {
+        index++;
+        iterator(result, item.value, onlyOnce(callback));
+      }
+    }
+    return index;
+  }
+
+  /**
+   * @private
+   */
+  function arrayEachFunc(array, createCallback) {
+    var index = -1;
+    var size = array.length;
+
+    while (++index < size) {
+      array[index](createCallback(index));
+    }
+  }
+
+  /**
+   * @private
+   */
+  function baseEachFunc(object, createCallback, keys) {
+    var key;
+    var index = -1;
+    var size = keys.length;
+
+    while (++index < size) {
+      key = keys[index];
+      object[key](createCallback(key));
+    }
+  }
+
+  /**
+   * @private
+   */
+  function arrayEachIndex(array, iterator, createCallback) {
+    var index = -1;
+    var size = array.length;
+
+    if (iterator.length === 3) {
+      while (++index < size) {
+        iterator(array[index], index, createCallback(index));
+      }
+    } else {
+      while (++index < size) {
+        iterator(array[index], createCallback(index));
+      }
+    }
+  }
+
+  /**
+   * @private
+   */
+  function baseEachIndex(object, iterator, createCallback, keys) {
+    var key;
+    var index = -1;
+    var size = keys.length;
+
+    if (iterator.length === 3) {
+      while (++index < size) {
+        key = keys[index];
+        iterator(object[key], key, createCallback(index));
+      }
+    } else {
+      while (++index < size) {
+        iterator(object[keys[index]], createCallback(index));
+      }
+    }
+  }
+
+  /**
+   * @private
+   */
+  function symbolEachIndex(collection, iterator, createCallback) {
+    var item;
+    var index = 0;
+    var iter = collection[iteratorSymbol]();
+
+    if (iterator.length === 3) {
+      while ((item = iter.next()).done === false) {
+        iterator(item.value, index, createCallback(index++));
+      }
+    } else {
+      while ((item = iter.next()).done === false) {
+        iterator(item.value, createCallback(index++));
+      }
+    }
+    return index;
+  }
+
+  /**
+   * @private
+   */
+  function baseEachKey(object, iterator, createCallback, keys) {
+    var key;
+    var index = -1;
+    var size = keys.length;
+
+    if (iterator.length === 3) {
+      while (++index < size) {
+        key = keys[index];
+        iterator(object[key], key, createCallback(key));
+      }
+    } else {
+      while (++index < size) {
+        key = keys[index];
+        iterator(object[key], createCallback(key));
+      }
+    }
+  }
+
+  /**
+   * @private
+   */
+  function symbolEachKey(collection, iterator, createCallback) {
+    var item;
+    var index = 0;
+    var iter = collection[iteratorSymbol]();
+
+    if (iterator.length === 3) {
+      while ((item = iter.next()).done === false) {
+        iterator(item.value, index, createCallback(index++));
+      }
+    } else {
+      while ((item = iter.next()).done === false) {
+        iterator(item.value, createCallback(index++));
+      }
+    }
+    return index;
+  }
+
+  /**
+   * @private
+   */
+  function arrayEachValue(array, iterator, createCallback) {
+    var value;
+    var index = -1;
+    var size = array.length;
+
+    if (iterator.length === 3) {
+      while (++index < size) {
+        value = array[index];
+        iterator(value, index, createCallback(value));
+      }
+    } else {
+      while (++index < size) {
+        value = array[index];
+        iterator(value, createCallback(value));
+      }
+    }
+  }
+
+  /**
+   * @private
+   */
+  function baseEachValue(object, iterator, createCallback, keys) {
+    var key, value;
+    var index = -1;
+    var size = keys.length;
+
+    if (iterator.length === 3) {
+      while (++index < size) {
+        key = keys[index];
+        value = object[key];
+        iterator(value, key, createCallback(value));
+      }
+    } else {
+      while (++index < size) {
+        value = object[keys[index]];
+        iterator(value, createCallback(value));
+      }
+    }
+  }
+
+  /**
+   * @private
+   */
+  function symbolEachValue(collection, iterator, createCallback) {
+    var value, item;
+    var index = 0;
+    var iter = collection[iteratorSymbol]();
+
+    if (iterator.length === 3) {
+      while ((item = iter.next()).done === false) {
+        value = item.value;
+        iterator(value, index++, createCallback(value));
+      }
+    } else {
+      while ((item = iter.next()).done === false) {
+        index++;
+        value = item.value;
+        iterator(value, createCallback(value));
+      }
+    }
+    return index;
+  }
+
+  /**
+   * @private
+   */
+  function arrayEachIndexValue(array, iterator, createCallback) {
+    var value;
+    var index = -1;
+    var size = array.length;
+
+    if (iterator.length === 3) {
+      while (++index < size) {
+        value = array[index];
+        iterator(value, index, createCallback(index, value));
+      }
+    } else {
+      while (++index < size) {
+        value = array[index];
+        iterator(value, createCallback(index, value));
+      }
+    }
+  }
+
+  /**
+   * @private
+   */
+  function baseEachIndexValue(object, iterator, createCallback, keys) {
+    var key, value;
+    var index = -1;
+    var size = keys.length;
+
+    if (iterator.length === 3) {
+      while (++index < size) {
+        key = keys[index];
+        value = object[key];
+        iterator(value, key, createCallback(index, value));
+      }
+    } else {
+      while (++index < size) {
+        value = object[keys[index]];
+        iterator(value, createCallback(index, value));
+      }
+    }
+  }
+
+  /**
+   * @private
+   */
+  function symbolEachIndexValue(collection, iterator, createCallback) {
+    var value, item;
+    var index = 0;
+    var iter = collection[iteratorSymbol]();
+
+    if (iterator.length === 3) {
+      while ((item = iter.next()).done === false) {
+        value = item.value;
+        iterator(value, index, createCallback(index++, value));
+      }
+    } else {
+      while ((item = iter.next()).done === false) {
+        value = item.value;
+        iterator(value, createCallback(index++, value));
+      }
+    }
+    return index;
+  }
+
+  /**
+   * @private
+   */
+  function baseEachKeyValue(object, iterator, createCallback, keys) {
+    var key, value;
+    var index = -1;
+    var size = keys.length;
+
+    if (iterator.length === 3) {
+      while (++index < size) {
+        key = keys[index];
+        value = object[key];
+        iterator(value, key, createCallback(key, value));
+      }
+    } else {
+      while (++index < size) {
+        key = keys[index];
+        value = object[key];
+        iterator(value, createCallback(key, value));
+      }
+    }
+  }
+
+  /**
+   * @private
+   */
+  function symbolEachKeyValue(collection, iterator, createCallback) {
+    var value, item;
+    var index = 0;
+    var iter = collection[iteratorSymbol]();
+
+    if (iterator.length === 3) {
+      while ((item = iter.next()).done === false) {
+        value = item.value;
+        iterator(value, index, createCallback(index++, value));
+      }
+    } else {
+      while ((item = iter.next()).done === false) {
+        value = item.value;
+        iterator(value, createCallback(index++, value));
+      }
+    }
+    return index;
+  }
+
+  /**
+   * @private
+   * @param {Function} func
+   */
+  function onlyOnce(func) {
+    return function(err, res) {
+      var fn = func;
+      func = throwError;
+      fn(err, res);
+    };
+  }
+
+  /**
+   * @private
+   * @param {Function} func
+   */
+  function once(func) {
+    return function(err, res) {
+      var fn = func;
+      func = noop;
+      fn(err, res);
+    };
+  }
+
+  /**
+   * @private
+   * @param {Function} arrayEach
+   * @param {Function} baseEach
+   */
+  function createEach(arrayEach, baseEach, symbolEach) {
+    return function each(collection, iterator, callback) {
+      callback = once(callback || noop);
+      var size, keys;
+      var completed = 0;
+      if (isArray(collection)) {
+        size = collection.length;
+        arrayEach(collection, iterator, done);
+      } else if (!collection) {
+      } else if (iteratorSymbol && collection[iteratorSymbol]) {
+        size = symbolEach(collection, iterator, done);
+        size && size === completed && callback(null);
+      } else if (typeof collection === obj) {
+        keys = nativeKeys(collection);
+        size = keys.length;
+        baseEach(collection, iterator, done, keys);
+      }
+      if (!size) {
+        callback(null);
+      }
+
+      function done(err, bool) {
+        if (err) {
+          callback = once(callback);
+          callback(err);
+        } else if (++completed === size) {
+          callback(null);
+        } else if (bool === false) {
+          callback = once(callback);
+          callback(null);
+        }
+      }
+    };
+  }
+
+  /**
+   * @private
+   * @param {Function} arrayEach
+   * @param {Function} baseEach
+   * @param {Function} symbolEach
+   */
+  function createMap(arrayEach, baseEach, symbolEach, useArray) {
+    var init, clone;
+    if (useArray) {
+      init = Array;
+      clone = createArray;
+    } else {
+      init = function() {
+        return {};
+      };
+      clone = objectClone;
+    }
+
+    return function(collection, iterator, callback) {
+      callback = callback || noop;
+      var size, keys, result;
+      var completed = 0;
+
+      if (isArray(collection)) {
+        size = collection.length;
+        result = init(size);
+        arrayEach(collection, iterator, createCallback);
+      } else if (!collection) {
+      } else if (iteratorSymbol && collection[iteratorSymbol]) {
+        // TODO: size could be changed
+        result = init(0);
+        size = symbolEach(collection, iterator, createCallback);
+        size && size === completed && callback(null, result);
+      } else if (typeof collection === obj) {
+        keys = nativeKeys(collection);
+        size = keys.length;
+        result = init(size);
+        baseEach(collection, iterator, createCallback, keys);
+      }
+      if (!size) {
+        callback(null, init());
+      }
+
+      function createCallback(key) {
+        return function done(err, res) {
+          if (key === null) {
+            throwError();
+          }
+          if (err) {
+            key = null;
+            callback = once(callback);
+            callback(err, clone(result));
+            return;
+          }
+          result[key] = res;
+          key = null;
+          if (++completed === size) {
+            callback(null, result);
+          }
+        };
+      }
+    };
+  }
+
+  /**
+   * @private
+   * @param {Function} arrayEach
+   * @param {Function} baseEach
+   * @param {Function} symbolEach
+   * @param {boolean} bool
+   */
+  function createFilter(arrayEach, baseEach, symbolEach, bool) {
+    return function(collection, iterator, callback) {
+      callback = callback || noop;
+      var size, keys, result;
+      var completed = 0;
+
+      if (isArray(collection)) {
+        size = collection.length;
+        result = Array(size);
+        arrayEach(collection, iterator, createCallback);
+      } else if (!collection) {
+      } else if (iteratorSymbol && collection[iteratorSymbol]) {
+        result = [];
+        size = symbolEach(collection, iterator, createCallback);
+        size && size === completed && callback(null, compact(result));
+      } else if (typeof collection === obj) {
+        keys = nativeKeys(collection);
+        size = keys.length;
+        result = Array(size);
+        baseEach(collection, iterator, createCallback, keys);
+      }
+      if (!size) {
+        return callback(null, []);
+      }
+
+      function createCallback(index, value) {
+        return function done(err, res) {
+          if (index === null) {
+            throwError();
+          }
+          if (err) {
+            index = null;
+            callback = once(callback);
+            callback(err);
+            return;
+          }
+          if (!!res === bool) {
+            result[index] = value;
+          }
+          index = null;
+          if (++completed === size) {
+            callback(null, compact(result));
+          }
+        };
+      }
+    };
+  }
+
+  /**
+   * @private
+   * @param {boolean} bool
+   */
+  function createFilterSeries(bool) {
+    return function(collection, iterator, callback) {
+      callback = onlyOnce(callback || noop);
+      var size, key, value, keys, iter, item, iterate;
+      var sync = false;
+      var completed = 0;
+      var result = [];
+
+      if (isArray(collection)) {
+        size = collection.length;
+        iterate = iterator.length === 3 ? arrayIteratorWithIndex : arrayIterator;
+      } else if (!collection) {
+      } else if (iteratorSymbol && collection[iteratorSymbol]) {
+        size = Infinity;
+        iter = collection[iteratorSymbol]();
+        iterate = iterator.length === 3 ? symbolIteratorWithKey : symbolIterator;
+      } else if (typeof collection === obj) {
+        keys = nativeKeys(collection);
+        size = keys.length;
+        iterate = iterator.length === 3 ? objectIteratorWithKey : objectIterator;
+      }
+      if (!size) {
+        return callback(null, []);
+      }
+      iterate();
+
+      function arrayIterator() {
+        value = collection[completed];
+        iterator(value, done);
+      }
+
+      function arrayIteratorWithIndex() {
+        value = collection[completed];
+        iterator(value, completed, done);
+      }
+
+      function symbolIterator() {
+        item = iter.next();
+        value = item.value;
+        item.done ? callback(null, result) : iterator(value, done);
+      }
+
+      function symbolIteratorWithKey() {
+        item = iter.next();
+        value = item.value;
+        item.done ? callback(null, result) : iterator(value, completed, done);
+      }
+
+      function objectIterator() {
+        key = keys[completed];
+        value = collection[key];
+        iterator(value, done);
+      }
+
+      function objectIteratorWithKey() {
+        key = keys[completed];
+        value = collection[key];
+        iterator(value, key, done);
+      }
+
+      function done(err, res) {
+        if (err) {
+          callback(err);
+          return;
+        }
+        if (!!res === bool) {
+          result[result.length] = value;
+        }
+        if (++completed === size) {
+          iterate = throwError;
+          callback(null, result);
+        } else if (sync) {
+          nextTick(iterate);
+        } else {
+          sync = true;
+          iterate();
+        }
+        sync = false;
+      }
+    };
+  }
+
+  /**
+   * @private
+   * @param {boolean} bool
+   */
+  function createFilterLimit(bool) {
+    return function(collection, limit, iterator, callback) {
+      callback = callback || noop;
+      var size, index, key, value, keys, iter, item, iterate, result;
+      var sync = false;
+      var started = 0;
+      var completed = 0;
+
+      if (isArray(collection)) {
+        size = collection.length;
+        iterate = iterator.length === 3 ? arrayIteratorWithIndex : arrayIterator;
+      } else if (!collection) {
+      } else if (iteratorSymbol && collection[iteratorSymbol]) {
+        size = Infinity;
+        result = [];
+        iter = collection[iteratorSymbol]();
+        iterate = iterator.length === 3 ? symbolIteratorWithKey : symbolIterator;
+      } else if (typeof collection === obj) {
+        keys = nativeKeys(collection);
+        size = keys.length;
+        iterate = iterator.length === 3 ? objectIteratorWithKey : objectIterator;
+      }
+      if (!size || isNaN(limit) || limit < 1) {
+        return callback(null, []);
+      }
+      result = result || Array(size);
+      timesSync(limit > size ? size : limit, iterate);
+
+      function arrayIterator() {
+        index = started++;
+        if (index < size) {
+          value = collection[index];
+          iterator(value, createCallback(value, index));
+        }
+      }
+
+      function arrayIteratorWithIndex() {
+        index = started++;
+        if (index < size) {
+          value = collection[index];
+          iterator(value, index, createCallback(value, index));
+        }
+      }
+
+      function symbolIterator() {
+        item = iter.next();
+        if (item.done === false) {
+          value = item.value;
+          iterator(value, createCallback(value, started++));
+        } else if (completed === started && iterator !== noop) {
+          iterator = noop;
+          callback(null, compact(result));
+        }
+      }
+
+      function symbolIteratorWithKey() {
+        item = iter.next();
+        if (item.done === false) {
+          value = item.value;
+          iterator(value, started, createCallback(value, started++));
+        } else if (completed === started && iterator !== noop) {
+          iterator = noop;
+          callback(null, compact(result));
+        }
+      }
+
+      function objectIterator() {
+        index = started++;
+        if (index < size) {
+          value = collection[keys[index]];
+          iterator(value, createCallback(value, index));
+        }
+      }
+
+      function objectIteratorWithKey() {
+        index = started++;
+        if (index < size) {
+          key = keys[index];
+          value = collection[key];
+          iterator(value, key, createCallback(value, index));
+        }
+      }
+
+      function createCallback(value, index) {
+        return function(err, res) {
+          if (index === null) {
+            throwError();
+          }
+          if (err) {
+            index = null;
+            iterate = noop;
+            callback = once(callback);
+            callback(err);
+            return;
+          }
+          if (!!res === bool) {
+            result[index] = value;
+          }
+          index = null;
+          if (++completed === size) {
+            callback = onlyOnce(callback);
+            callback(null, compact(result));
+          } else if (sync) {
+            nextTick(iterate);
+          } else {
+            sync = true;
+            iterate();
+          }
+          sync = false;
+        };
+      }
+    };
+  }
+
+  /**
+   * @memberof async
+   * @namespace eachSeries
+   * @param {Array|Object} collection
+   * @param {Function} iterator
+   * @param {Function} callback
+   * @example
+   *
+   * // array
+   * var order = [];
+   * var array = [1, 3, 2];
+   * var iterator = function(num, done) {
+   *   setTimeout(function() {
+   *     order.push(num);
+   *     done();
+   *   }, num * 10);
+   * };
+   * async.eachSeries(array, iterator, function(err, res) {
+   *   console.log(res); // undefined
+   *   console.log(order); // [1, 3, 2]
+   * });
+   *
+   * @example
+   *
+   * // array with index
+   * var order = [];
+   * var array = [1, 3, 2];
+   * var iterator = function(num, index, done) {
+   *   setTimeout(function() {
+   *     order.push([num, index]);
+   *     done();
+   *   }, num * 10);
+   * };
+   * async.eachSeries(array, iterator, function(err, res) {
+   *   console.log(res); // undefined
+   *   console.log(order); // [[1, 0], [3, 1], [2, 2]]
+   * });
+   *
+   * @example
+   *
+   * // object
+   * var order = [];
+   * var object = { a: 1, b: 3, c: 2 };
+   * var iterator = function(num, done) {
+   *   setTimeout(function() {
+   *     order.push(num);
+   *     done();
+   *   }, num * 10);
+   * };
+   * async.eachSeries(object, iterator, function(err, res) {
+   *   console.log(res); // undefined
+   *   console.log(order); // [1, 3, 2]
+   * });
+   *
+   * @example
+   *
+   * // object with key
+   * var order = [];
+   * var object = { a: 1, b: 3, c: 2 };
+   * var iterator = function(num, key, done) {
+   *   setTimeout(function() {
+   *     order.push([num, key]);
+   *     done();
+   *   }, num * 10);
+   * };
+   * async.eachSeries(object, iterator, function(err, res) {
+   *   console.log(res); // undefined
+   *   console.log(order); // [[1, 'a'], [3, 'b'], [2, 'b']]
+   * });
+   *
+   * @example
+   *
+   * // break
+   * var order = [];
+   * var array = [1, 3, 2];
+   * var iterator = function(num, done) {
+   *   setTimeout(function() {
+   *     order.push(num);
+   *     done(null, num !== 3);
+   *   }, num * 10);
+   * };
+   * async.eachSeries(array, iterator, function(err, res) {
+   *   console.log(res); // undefined
+   *   console.log(order); // [1, 3]
+   * });
+   */
+  function eachSeries(collection, iterator, callback) {
+    callback = onlyOnce(callback || noop);
+    var size, key, keys, iter, item, iterate;
+    var sync = false;
+    var completed = 0;
+
+    if (isArray(collection)) {
+      size = collection.length;
+      iterate = iterator.length === 3 ? arrayIteratorWithIndex : arrayIterator;
+    } else if (!collection) {
+    } else if (iteratorSymbol && collection[iteratorSymbol]) {
+      size = Infinity;
+      iter = collection[iteratorSymbol]();
+      iterate = iterator.length === 3 ? symbolIteratorWithKey : symbolIterator;
+    } else if (typeof collection === obj) {
+      keys = nativeKeys(collection);
+      size = keys.length;
+      iterate = iterator.length === 3 ? objectIteratorWithKey : objectIterator;
+    }
+    if (!size) {
+      return callback(null);
+    }
+    iterate();
+
+    function arrayIterator() {
+      iterator(collection[completed], done);
+    }
+
+    function arrayIteratorWithIndex() {
+      iterator(collection[completed], completed, done);
+    }
+
+    function symbolIterator() {
+      item = iter.next();
+      item.done ? callback(null) : iterator(item.value, done);
+    }
+
+    function symbolIteratorWithKey() {
+      item = iter.next();
+      item.done ? callback(null) : iterator(item.value, completed, done);
+    }
+
+    function objectIterator() {
+      iterator(collection[keys[completed]], done);
+    }
+
+    function objectIteratorWithKey() {
+      key = keys[completed];
+      iterator(collection[key], key, done);
+    }
+
+    function done(err, bool) {
+      if (err) {
+        callback(err);
+      } else if (++completed === size || bool === false) {
+        iterate = throwError;
+        callback(null);
+      } else if (sync) {
+        nextTick(iterate);
+      } else {
+        sync = true;
+        iterate();
+      }
+      sync = false;
+    }
+  }
+
+  /**
+   * @memberof async
+   * @namespace eachLimit
+   * @param {Array|Object} collection
+   * @param {number} limit - limit >= 1
+   * @param {Function} iterator
+   * @param {Function} callback
+   * @example
+   *
+   * // array
+   * var order = [];
+   * var array = [1, 5, 3, 4, 2];
+   * var iterator = function(num, done) {
+   *   setTimeout(function() {
+   *     order.push(num);
+   *     done();
+   *   }, num * 10);
+   * };
+   * async.eachLimit(array, 2, iterator, function(err, res) {
+   *   console.log(res); // undefined
+   *   console.log(order); // [1, 3, 5, 2, 4]
+   * });
+   *
+   * @example
+   *
+   * // array with index
+   * var order = [];
+   * var array = [1, 5, 3, 4, 2];
+   * var iterator = function(num, index, done) {
+   *   setTimeout(function() {
+   *     order.push([num, index]);
+   *     done();
+   *   }, num * 10);
+   * };
+   * async.eachLimit(array, 2, iterator, function(err, res) {
+   *   console.log(res); // undefined
+   *   console.log(order); // [[1, 0], [3, 2], [5, 1], [2, 4], [4, 3]]
+   * });
+   *
+   * @example
+   *
+   * // object
+   * var order = [];
+   * var object = { a: 1, b: 5, c: 3, d: 4, e: 2 };
+   * var iterator = function(num, done) {
+   *   setTimeout(function() {
+   *     order.push(num);
+   *     done();
+   *   }, num * 10);
+   * };
+   * async.eachLimit(object, 2, iterator, function(err, res) {
+   *   console.log(res); // undefined
+   *   console.log(order); // [1, 3, 5, 2, 4]
+   * });
+   *
+   * @example
+   *
+   * // object with key
+   * var order = [];
+   * var object = { a: 1, b: 5, c: 3, d: 4, e: 2 };
+   * var iterator = function(num, key, done) {
+   *   setTimeout(function() {
+   *     order.push([num, key]);
+   *     done();
+   *   }, num * 10);
+   * };
+   * async.eachLimit(object, 2, iterator, function(err, res) {
+   *   console.log(res); // undefined
+   *   console.log(order); // [[1, 'a'], [3, 'c'], [5, 'b'], [2, 'e'], [4, 'd']]
+   * });
+   *
+   * @example
+   *
+   * // break
+   * var order = [];
+   * var array = [1, 5, 3, 4, 2];
+   * var iterator = function(num, done) {
+   *   setTimeout(function() {
+   *     order.push(num);
+   *     done(null, num !== 5);
+   *   }, num * 10);
+   * };
+   * async.eachLimit(array, 2, iterator, function(err, res) {
+   *   console.log(res); // undefined
+   *   console.log(order); // [1, 3, 5]
+   * });
+   *
+   */
+  function eachLimit(collection, limit, iterator, callback) {
+    callback = callback || noop;
+    var size, index, key, keys, iter, item, iterate;
+    var sync = false;
+    var started = 0;
+    var completed = 0;
+
+    if (isArray(collection)) {
+      size = collection.length;
+      iterate = iterator.length === 3 ? arrayIteratorWithIndex : arrayIterator;
+    } else if (!collection) {
+    } else if (iteratorSymbol && collection[iteratorSymbol]) {
+      size = Infinity;
+      iter = collection[iteratorSymbol]();
+      iterate = iterator.length === 3 ? symbolIteratorWithKey : symbolIterator;
+    } else if (typeof collection === obj) {
+      keys = nativeKeys(collection);
+      size = keys.length;
+      iterate = iterator.length === 3 ? objectIteratorWithKey : objectIterator;
+    } else {
+      return callback(null);
+    }
+    if (!size || isNaN(limit) || limit < 1) {
+      return callback(null);
+    }
+    timesSync(limit > size ? size : limit, iterate);
+
+    function arrayIterator() {
+      if (started < size) {
+        iterator(collection[started++], done);
+      }
+    }
+
+    function arrayIteratorWithIndex() {
+      index = started++;
+      if (index < size) {
+        iterator(collection[index], index, done);
+      }
+    }
+
+    function symbolIterator() {
+      item = iter.next();
+      if (item.done === false) {
+        started++;
+        iterator(item.value, done);
+      } else if (completed === started && iterator !== noop) {
+        iterator = noop;
+        callback(null);
+      }
+    }
+
+    function symbolIteratorWithKey() {
+      item = iter.next();
+      if (item.done === false) {
+        iterator(item.value, started++, done);
+      } else if (completed === started && iterator !== noop) {
+        iterator = noop;
+        callback(null);
+      }
+    }
+
+    function objectIterator() {
+      if (started < size) {
+        iterator(collection[keys[started++]], done);
+      }
+    }
+
+    function objectIteratorWithKey() {
+      index = started++;
+      if (index < size) {
+        key = keys[index];
+        iterator(collection[key], key, done);
+      }
+    }
+
+    function done(err, bool) {
+      if (err || bool === false) {
+        iterate = noop;
+        callback = once(callback);
+        callback(err);
+      } else if (++completed === size) {
+        iterator = noop;
+        iterate = throwError;
+        callback = onlyOnce(callback);
+        callback(null);
+      } else if (sync) {
+        nextTick(iterate);
+      } else {
+        sync = true;
+        iterate();
+      }
+      sync = false;
+    }
+  }
+
+  /**
+   * @memberof async
+   * @namespace mapSeries
+   * @param {Array|Object} collection
+   * @param {Function} iterator
+   * @param {Function} callback
+   * @example
+   *
+   * // array
+   * var order = [];
+   * var array = [1, 3, 2];
+   * var iterator = function(num, done) {
+   *   setTimeout(function() {
+   *     order.push(num);
+   *     done(null, num);
+   *   }, num * 10);
+   * };
+   * async.mapSeries(array, iterator, function(err, res) {
+   *   console.log(res); // [1, 3, 2];
+   *   console.log(order); // [1, 3, 2]
+   * });
+   *
+   * @example
+   *
+   * // array with index
+   * var order = [];
+   * var array = [1, 3, 2];
+   * var iterator = function(num, index, done) {
+   *   setTimeout(function() {
+   *     order.push([num, index]);
+   *     done(null, num);
+   *   }, num * 10);
+   * };
+   * async.mapSeries(array, iterator, function(err, res) {
+   *   console.log(res); // [1, 3, 2]
+   *   console.log(order); // [[1, 0], [3, 1], [2, 2]]
+   * });
+   *
+   * @example
+   *
+   * // object
+   * var order = [];
+   * var object = { a: 1, b: 3, c: 2 };
+   * var iterator = function(num, done) {
+   *   setTimeout(function() {
+   *     order.push(num);
+   *     done(null, num);
+   *   }, num * 10);
+   * };
+   * async.mapSeries(object, iterator, function(err, res) {
+   *   console.log(res); // [1, 3, 2]
+   *   console.log(order); // [1, 3, 2]
+   * });
+   *
+   * @example
+   *
+   * // object with key
+   * var order = [];
+   * var object = { a: 1, b: 3, c: 2 };
+   * var iterator = function(num, key, done) {
+   *   setTimeout(function() {
+   *     order.push([num, key]);
+   *     done(null, num);
+   *   }, num * 10);
+   * };
+   * async.mapSeries(object, iterator, function(err, res) {
+   *   console.log(res); // [1, 3, 2]
+   *   console.log(order); // [[1, 'a'], [3, 'b'], [2, 'c']]
+   * });
+   *
+   */
+  function mapSeries(collection, iterator, callback) {
+    callback = callback || noop;
+    var size, key, keys, iter, item, result, iterate;
+    var sync = false;
+    var completed = 0;
+
+    if (isArray(collection)) {
+      size = collection.length;
+      iterate = iterator.length === 3 ? arrayIteratorWithIndex : arrayIterator;
+    } else if (!collection) {
+    } else if (iteratorSymbol && collection[iteratorSymbol]) {
+      size = Infinity;
+      result = [];
+      iter = collection[iteratorSymbol]();
+      iterate = iterator.length === 3 ? symbolIteratorWithKey : symbolIterator;
+    } else if (typeof collection === obj) {
+      keys = nativeKeys(collection);
+      size = keys.length;
+      iterate = iterator.length === 3 ? objectIteratorWithKey : objectIterator;
+    }
+    if (!size) {
+      return callback(null, []);
+    }
+    result = result || Array(size);
+    iterate();
+
+    function arrayIterator() {
+      iterator(collection[completed], done);
+    }
+
+    function arrayIteratorWithIndex() {
+      iterator(collection[completed], completed, done);
+    }
+
+    function symbolIterator() {
+      item = iter.next();
+      item.done ? callback(null, result) : iterator(item.value, done);
+    }
+
+    function symbolIteratorWithKey() {
+      item = iter.next();
+      item.done ? callback(null, result) : iterator(item.value, completed, done);
+    }
+
+    function objectIterator() {
+      iterator(collection[keys[completed]], done);
+    }
+
+    function objectIteratorWithKey() {
+      key = keys[completed];
+      iterator(collection[key], key, done);
+    }
+
+    function done(err, res) {
+      if (err) {
+        iterate = throwError;
+        callback = onlyOnce(callback);
+        callback(err, createArray(result));
+        return;
+      }
+      result[completed] = res;
+      if (++completed === size) {
+        iterate = throwError;
+        callback(null, result);
+        callback = throwError;
+      } else if (sync) {
+        nextTick(iterate);
+      } else {
+        sync = true;
+        iterate();
+      }
+      sync = false;
+    }
+  }
+
+  /**
+   * @memberof async
+   * @namespace mapLimit
+   * @param {Array|Object} collection
+   * @param {number} limit - limit >= 1
+   * @param {Function} iterator
+   * @param {Function} callback
+   * @example
+   *
+   * // array
+   * var order = [];
+   * var array = [1, 5, 3, 4, 2];
+   * var iterator = function(num, done) {
+   *   setTimeout(function() {
+   *     order.push(num);
+   *     done(null, num);
+   *   }, num * 10);
+   * };
+   * async.mapLimit(array, 2, iterator, function(err, res) {
+   *   console.log(res); // [1, 5, 3, 4, 2]
+   *   console.log(order); // [1, 3, 5, 2, 4]
+   * });
+   *
+   * @example
+   *
+   * // array with index
+   * var order = [];
+   * var array = [1, 5, 3, 4, 2];
+   * var iterator = function(num, index, done) {
+   *   setTimeout(function() {
+   *     order.push([num, index]);
+   *     done(null, num);
+   *   }, num * 10);
+   * };
+   * async.mapLimit(array, 2, iterator, function(err, res) {
+   *   console.log(res); // [1, 5, 3, 4, 2]
+   *   console.log(order); // [[1, 0], [3, 2], [5, 1], [2, 4], [4, 3]]
+   * });
+   *
+   * @example
+   *
+   * // object
+   * var order = [];
+   * var object = { a: 1, b: 5, c: 3, d: 4, e: 2 };
+   * var iterator = function(num, done) {
+   *   setTimeout(function() {
+   *     order.push(num);
+   *     done(null, num);
+   *   }, num * 10);
+   * };
+   * async.mapLimit(object, 2, iterator, function(err, res) {
+   *   console.log(res); // [1, 5, 3, 4, 2]
+   *   console.log(order); // [1, 3, 5, 2, 4]
+   * });
+   *
+   * @example
+   *
+   * // object with key
+   * var order = [];
+   * var object = { a: 1, b: 5, c: 3, d: 4, e: 2 };
+   * var iterator = function(num, key, done) {
+   *   setTimeout(function() {
+   *     order.push([num, key]);
+   *     done(null, num);
+   *   }, num * 10);
+   * };
+   * async.mapLimit(object, 2, iterator, function(err, res) {
+   *   console.log(res); // [1, 5, 3, 4, 2]
+   *   console.log(order); // [[1, 'a'], [3, 'c'], [5, 'b'], [2, 'e'], [4, 'd']]
+   * });
+   *
+   */
+  function mapLimit(collection, limit, iterator, callback) {
+    callback = callback || noop;
+    var size, index, key, keys, iter, item, result, iterate;
+    var sync = false;
+    var started = 0;
+    var completed = 0;
+
+    if (isArray(collection)) {
+      size = collection.length;
+      iterate = iterator.length === 3 ? arrayIteratorWithIndex : arrayIterator;
+    } else if (!collection) {
+    } else if (iteratorSymbol && collection[iteratorSymbol]) {
+      size = Infinity;
+      result = [];
+      iter = collection[iteratorSymbol]();
+      iterate = iterator.length === 3 ? symbolIteratorWithKey : symbolIterator;
+    } else if (typeof collection === obj) {
+      keys = nativeKeys(collection);
+      size = keys.length;
+      iterate = iterator.length === 3 ? objectIteratorWithKey : objectIterator;
+    }
+    if (!size || isNaN(limit) || limit < 1) {
+      return callback(null, []);
+    }
+    result = result || Array(size);
+    timesSync(limit > size ? size : limit, iterate);
+
+    function arrayIterator() {
+      index = started++;
+      if (index < size) {
+        iterator(collection[index], createCallback(index));
+      }
+    }
+
+    function arrayIteratorWithIndex() {
+      index = started++;
+      if (index < size) {
+        iterator(collection[index], index, createCallback(index));
+      }
+    }
+
+    function symbolIterator() {
+      item = iter.next();
+      if (item.done === false) {
+        iterator(item.value, createCallback(started++));
+      } else if (completed === started && iterator !== noop) {
+        iterator = noop;
+        callback(null, result);
+      }
+    }
+
+    function symbolIteratorWithKey() {
+      item = iter.next();
+      if (item.done === false) {
+        iterator(item.value, started, createCallback(started++));
+      } else if (completed === started && iterator !== noop) {
+        iterator = noop;
+        callback(null, result);
+      }
+    }
+
+    function objectIterator() {
+      index = started++;
+      if (index < size) {
+        iterator(collection[keys[index]], createCallback(index));
+      }
+    }
+
+    function objectIteratorWithKey() {
+      index = started++;
+      if (index < size) {
+        key = keys[index];
+        iterator(collection[key], key, createCallback(index));
+      }
+    }
+
+    function createCallback(index) {
+      return function(err, res) {
+        if (index === null) {
+          throwError();
+        }
+        if (err) {
+          index = null;
+          iterate = noop;
+          callback = once(callback);
+          callback(err, createArray(result));
+          return;
+        }
+        result[index] = res;
+        index = null;
+        if (++completed === size) {
+          iterate = throwError;
+          callback(null, result);
+          callback = throwError;
+        } else if (sync) {
+          nextTick(iterate);
+        } else {
+          sync = true;
+          iterate();
+        }
+        sync = false;
+      };
+    }
+  }
+
+  /**
+   * @memberof async
+   * @namespace mapValuesSeries
+   * @param {Array|Object} collection
+   * @param {Function} iterator
+   * @param {Function} callback
+   * @example
+   *
+   * // array
+   * var order = [];
+   * var array = [1, 3, 2];
+   * var iterator = function(num, done) {
+   *   setTimeout(function() {
+   *     order.push(num);
+   *     done(null, num);
+   *   }, num * 10);
+   * };
+   * async.mapValuesSeries(array, iterator, function(err, res) {
+   *   console.log(res); // { '0': 1, '1': 3, '2': 2 }
+   *   console.log(order); // [1, 3, 2]
+   * });
+   *
+   * @example
+   *
+   * // array with index
+   * var order = [];
+   * var array = [1, 3, 2];
+   * var iterator = function(num, index, done) {
+   *   setTimeout(function() {
+   *     order.push([num, index]);
+   *     done(null, num);
+   *   }, num * 10);
+   * };
+   * async.mapValuesSeries(array, iterator, function(err, res) {
+   *   console.log(res); // { '0': 1, '1': 3, '2': 2 }
+   *   console.log(order); // [[1, 0], [3, 1], [2, 2]]
+   * });
+   *
+   * @example
+   *
+   * // object
+   * var order = [];
+   * var object = { a: 1, b: 3, c: 2 };
+   * var iterator = function(num, done) {
+   *   setTimeout(function() {
+   *     order.push(num);
+   *     done(null, num);
+   *   }, num * 10);
+   * };
+   * async.mapValuesSeries(object, iterator, function(err, res) {
+   *   console.log(res); // { a: 1, b: 3, c: 2 }
+   *   console.log(order); // [1, 3, 2]
+   * });
+   *
+   * @example
+   *
+   * // object with key
+   * var order = [];
+   * var object = { a: 1, b: 3, c: 2 };
+   * var iterator = function(num, key, done) {
+   *   setTimeout(function() {
+   *     order.push([num, key]);
+   *     done(null, num);
+   *   }, num * 10);
+   * };
+   * async.mapValuesSeries(object, iterator, function(err, res) {
+   *   console.log(res); // { a: 1, b: 3, c: 2 }
+   *   console.log(order); // [[1, 'a'], [3, 'b'], [2, 'c']]
+   * });
+   *
+   */
+  function mapValuesSeries(collection, iterator, callback) {
+    callback = callback || noop;
+    var size, key, keys, iter, item, iterate;
+    var sync = false;
+    var result = {};
+    var completed = 0;
+
+    if (isArray(collection)) {
+      size = collection.length;
+      iterate = iterator.length === 3 ? arrayIteratorWithIndex : arrayIterator;
+    } else if (!collection) {
+    } else if (iteratorSymbol && collection[iteratorSymbol]) {
+      size = Infinity;
+      iter = collection[iteratorSymbol]();
+      iterate = iterator.length === 3 ? symbolIteratorWithKey : symbolIterator;
+    } else if (typeof collection === obj) {
+      keys = nativeKeys(collection);
+      size = keys.length;
+      iterate = iterator.length === 3 ? objectIteratorWithKey : objectIterator;
+    }
+    if (!size) {
+      return callback(null, result);
+    }
+    iterate();
+
+    function arrayIterator() {
+      key = completed;
+      iterator(collection[completed], done);
+    }
+
+    function arrayIteratorWithIndex() {
+      key = completed;
+      iterator(collection[completed], completed, done);
+    }
+
+    function symbolIterator() {
+      key = completed;
+      item = iter.next();
+      item.done ? callback(null, result) : iterator(item.value, done);
+    }
+
+    function symbolIteratorWithKey() {
+      key = completed;
+      item = iter.next();
+      item.done ? callback(null, result) : iterator(item.value, completed, done);
+    }
+
+    function objectIterator() {
+      key = keys[completed];
+      iterator(collection[key], done);
+    }
+
+    function objectIteratorWithKey() {
+      key = keys[completed];
+      iterator(collection[key], key, done);
+    }
+
+    function done(err, res) {
+      if (err) {
+        iterate = throwError;
+        callback = onlyOnce(callback);
+        callback(err, objectClone(result));
+        return;
+      }
+      result[key] = res;
+      if (++completed === size) {
+        iterate = throwError;
+        callback(null, result);
+        callback = throwError;
+      } else if (sync) {
+        nextTick(iterate);
+      } else {
+        sync = true;
+        iterate();
+      }
+      sync = false;
+    }
+  }
+
+  /**
+   * @memberof async
+   * @namespace mapValuesLimit
+   * @param {Array|Object} collection
+   * @param {number} limit - limit >= 1
+   * @param {Function} iterator
+   * @param {Function} callback
+   * @example
+   *
+   * // array
+   * var order = [];
+   * var array = [1, 5, 3, 4, 2];
+   * var iterator = function(num, done) {
+   *   setTimeout(function() {
+   *     order.push(num);
+   *     done(null, num);
+   *   }, num * 10);
+   * };
+   * async.mapValuesLimit(array, 2, iterator, function(err, res) {
+   *   console.log(res); // { '0': 1, '1': 5, '2': 3, '3': 4, '4': 2 }
+   *   console.log(order); // [1, 3, 5, 2, 4]
+   * });
+   *
+   * @example
+   *
+   * // array with index
+   * var order = [];
+   * var array = [1, 5, 3, 4, 2];
+   * var iterator = function(num, index, done) {
+   *   setTimeout(function() {
+   *     order.push([num, index]);
+   *     done(null, num);
+   *   }, num * 10);
+   * };
+   * async.mapValuesLimit(array, 2, iterator, function(err, res) {
+   *   console.log(res); // { '0': 1, '1': 5, '2': 3, '3': 4, '4': 2 }
+   *   console.log(order); // [[1, 0], [3, 2], [5, 1], [2, 4], [4, 3]]
+   * });
+   *
+   * @example
+   *
+   * // object
+   * var order = [];
+   * var object = { a: 1, b: 5, c: 3, d: 4, e: 2 };
+   * var iterator = function(num, done) {
+   *   setTimeout(function() {
+   *     order.push(num);
+   *     done(null, num);
+   *   }, num * 10);
+   * };
+   * async.mapValuesLimit(object, 2, iterator, function(err, res) {
+   *   console.log(res); // { a: 1, b: 5, c: 3, d: 4, e: 2 }
+   *   console.log(order); // [1, 3, 5, 2, 4]
+   * });
+   *
+   * @example
+   *
+   * // object with key
+   * var order = [];
+   * var object = { a: 1, b: 5, c: 3, d: 4, e: 2 };
+   * var iterator = function(num, key, done) {
+   *   setTimeout(function() {
+   *     order.push([num, key]);
+   *     done(null, num);
+   *   }, num * 10);
+   * };
+   * async.mapValuesLimit(object, 2, iterator, function(err, res) {
+   *   console.log(res); // { a: 1, b: 5, c: 3, d: 4, e: 2 }
+   *   console.log(order); // [[1, 'a'], [3, 'c'], [5, 'b'], [2, 'e'], [4, 'd']]
+   * });
+   *
+   */
+  function mapValuesLimit(collection, limit, iterator, callback) {
+    callback = callback || noop;
+    var size, index, key, keys, iter, item, iterate;
+    var sync = false;
+    var result = {};
+    var started = 0;
+    var completed = 0;
+
+    if (isArray(collection)) {
+      size = collection.length;
+      iterate = iterator.length === 3 ? arrayIteratorWithIndex : arrayIterator;
+    } else if (!collection) {
+    } else if (iteratorSymbol && collection[iteratorSymbol]) {
+      size = Infinity;
+      iter = collection[iteratorSymbol]();
+      iterate = iterator.length === 3 ? symbolIteratorWithKey : symbolIterator;
+    } else if (typeof collection === obj) {
+      keys = nativeKeys(collection);
+      size = keys.length;
+      iterate = iterator.length === 3 ? objectIteratorWithKey : objectIterator;
+    }
+    if (!size || isNaN(limit) || limit < 1) {
+      return callback(null, result);
+    }
+    timesSync(limit > size ? size : limit, iterate);
+
+    function arrayIterator() {
+      index = started++;
+      if (index < size) {
+        iterator(collection[index], createCallback(index));
+      }
+    }
+
+    function arrayIteratorWithIndex() {
+      index = started++;
+      if (index < size) {
+        iterator(collection[index], index, createCallback(index));
+      }
+    }
+
+    function symbolIterator() {
+      item = iter.next();
+      if (item.done === false) {
+        iterator(item.value, createCallback(started++));
+      } else if (completed === started && iterator !== noop) {
+        iterator = noop;
+        callback(null, result);
+      }
+    }
+
+    function symbolIteratorWithKey() {
+      item = iter.next();
+      if (item.done === false) {
+        iterator(item.value, started, createCallback(started++));
+      } else if (completed === started && iterator !== noop) {
+        iterator = noop;
+        callback(null, result);
+      }
+    }
+
+    function objectIterator() {
+      index = started++;
+      if (index < size) {
+        key = keys[index];
+        iterator(collection[key], createCallback(key));
+      }
+    }
+
+    function objectIteratorWithKey() {
+      index = started++;
+      if (index < size) {
+        key = keys[index];
+        iterator(collection[key], key, createCallback(key));
+      }
+    }
+
+    function createCallback(key) {
+      return function(err, res) {
+        if (key === null) {
+          throwError();
+        }
+        if (err) {
+          key = null;
+          iterate = noop;
+          callback = once(callback);
+          callback(err, objectClone(result));
+          return;
+        }
+        result[key] = res;
+        key = null;
+        if (++completed === size) {
+          callback(null, result);
+        } else if (sync) {
+          nextTick(iterate);
+        } else {
+          sync = true;
+          iterate();
+        }
+        sync = false;
+      };
+    }
+  }
+
+  /**
+   * @private
+   * @param {Function} arrayEach
+   * @param {Function} baseEach
+   * @param {Function} symbolEach
+   * @param {boolean} bool
+   */
+  function createDetect(arrayEach, baseEach, symbolEach, bool) {
+    return function(collection, iterator, callback) {
+      callback = callback || noop;
+      var size, keys;
+      var completed = 0;
+
+      if (isArray(collection)) {
+        size = collection.length;
+        arrayEach(collection, iterator, createCallback);
+      } else if (!collection) {
+      } else if (iteratorSymbol && collection[iteratorSymbol]) {
+        size = symbolEach(collection, iterator, createCallback);
+        size && size === completed && callback(null);
+      } else if (typeof collection === obj) {
+        keys = nativeKeys(collection);
+        size = keys.length;
+        baseEach(collection, iterator, createCallback, keys);
+      }
+      if (!size) {
+        callback(null);
+      }
+
+      function createCallback(value) {
+        var called = false;
+        return function done(err, res) {
+          if (called) {
+            throwError();
+          }
+          called = true;
+          if (err) {
+            callback = once(callback);
+            callback(err);
+          } else if (!!res === bool) {
+            callback = once(callback);
+            callback(null, value);
+          } else if (++completed === size) {
+            callback(null);
+          }
+        };
+      }
+    };
+  }
+
+  /**
+   * @private
+   * @param {boolean} bool
+   */
+  function createDetectSeries(bool) {
+    return function(collection, iterator, callback) {
+      callback = onlyOnce(callback || noop);
+      var size, key, value, keys, iter, item, iterate;
+      var sync = false;
+      var completed = 0;
+
+      if (isArray(collection)) {
+        size = collection.length;
+        iterate = iterator.length === 3 ? arrayIteratorWithIndex : arrayIterator;
+      } else if (!collection) {
+      } else if (iteratorSymbol && collection[iteratorSymbol]) {
+        size = Infinity;
+        iter = collection[iteratorSymbol]();
+        iterate = iterator.length === 3 ? symbolIteratorWithKey : symbolIterator;
+      } else if (typeof collection === obj) {
+        keys = nativeKeys(collection);
+        size = keys.length;
+        iterate = iterator.length === 3 ? objectIteratorWithKey : objectIterator;
+      }
+      if (!size) {
+        return callback(null);
+      }
+      iterate();
+
+      function arrayIterator() {
+        value = collection[completed];
+        iterator(value, done);
+      }
+
+      function arrayIteratorWithIndex() {
+        value = collection[completed];
+        iterator(value, completed, done);
+      }
+
+      function symbolIterator() {
+        item = iter.next();
+        value = item.value;
+        item.done ? callback(null) : iterator(value, done);
+      }
+
+      function symbolIteratorWithKey() {
+        item = iter.next();
+        value = item.value;
+        item.done ? callback(null) : iterator(value, completed, done);
+      }
+
+      function objectIterator() {
+        value = collection[keys[completed]];
+        iterator(value, done);
+      }
+
+      function objectIteratorWithKey() {
+        key = keys[completed];
+        value = collection[key];
+        iterator(value, key, done);
+      }
+
+      function done(err, res) {
+        if (err) {
+          callback(err);
+        } else if (!!res === bool) {
+          iterate = throwError;
+          callback(null, value);
+        } else if (++completed === size) {
+          iterate = throwError;
+          callback(null);
+        } else if (sync) {
+          nextTick(iterate);
+        } else {
+          sync = true;
+          iterate();
+        }
+        sync = false;
+      }
+    };
+  }
+
+  /**
+   * @private
+   * @param {boolean} bool
+   */
+  function createDetectLimit(bool) {
+    return function(collection, limit, iterator, callback) {
+      callback = callback || noop;
+      var size, index, key, value, keys, iter, item, iterate;
+      var sync = false;
+      var started = 0;
+      var completed = 0;
+
+      if (isArray(collection)) {
+        size = collection.length;
+        iterate = iterator.length === 3 ? arrayIteratorWithIndex : arrayIterator;
+      } else if (!collection) {
+      } else if (iteratorSymbol && collection[iteratorSymbol]) {
+        size = Infinity;
+        iter = collection[iteratorSymbol]();
+        iterate = iterator.length === 3 ? symbolIteratorWithKey : symbolIterator;
+      } else if (typeof collection === obj) {
+        keys = nativeKeys(collection);
+        size = keys.length;
+        iterate = iterator.length === 3 ? objectIteratorWithKey : objectIterator;
+      }
+      if (!size || isNaN(limit) || limit < 1) {
+        return callback(null);
+      }
+      timesSync(limit > size ? size : limit, iterate);
+
+      function arrayIterator() {
+        index = started++;
+        if (index < size) {
+          value = collection[index];
+          iterator(value, createCallback(value));
+        }
+      }
+
+      function arrayIteratorWithIndex() {
+        index = started++;
+        if (index < size) {
+          value = collection[index];
+          iterator(value, index, createCallback(value));
+        }
+      }
+
+      function symbolIterator() {
+        item = iter.next();
+        if (item.done === false) {
+          started++;
+          value = item.value;
+          iterator(value, createCallback(value));
+        } else if (completed === started && iterator !== noop) {
+          iterator = noop;
+          callback(null);
+        }
+      }
+
+      function symbolIteratorWithKey() {
+        item = iter.next();
+        if (item.done === false) {
+          value = item.value;
+          iterator(value, started++, createCallback(value));
+        } else if (completed === started && iterator !== noop) {
+          iterator = noop;
+          callback(null);
+        }
+      }
+
+      function objectIterator() {
+        index = started++;
+        if (index < size) {
+          value = collection[keys[index]];
+          iterator(value, createCallback(value));
+        }
+      }
+
+      function objectIteratorWithKey() {
+        if (started < size) {
+          key = keys[started++];
+          value = collection[key];
+          iterator(value, key, createCallback(value));
+        }
+      }
+
+      function createCallback(value) {
+        var called = false;
+        return function(err, res) {
+          if (called) {
+            throwError();
+          }
+          called = true;
+          if (err) {
+            iterate = noop;
+            callback = once(callback);
+            callback(err);
+          } else if (!!res === bool) {
+            iterate = noop;
+            callback = once(callback);
+            callback(null, value);
+          } else if (++completed === size) {
+            callback(null);
+          } else if (sync) {
+            nextTick(iterate);
+          } else {
+            sync = true;
+            iterate();
+          }
+          sync = false;
+        };
+      }
+    };
+  }
+
+  /**
+   * @private
+   * @param {Function} arrayEach
+   * @param {Function} baseEach
+   * @param {Function} symbolEach
+   * @param {boolean} bool
+   */
+  function createPick(arrayEach, baseEach, symbolEach, bool) {
+    return function(collection, iterator, callback) {
+      callback = callback || noop;
+      var size, keys;
+      var completed = 0;
+      var result = {};
+
+      if (isArray(collection)) {
+        size = collection.length;
+        arrayEach(collection, iterator, createCallback);
+      } else if (!collection) {
+      } else if (iteratorSymbol && collection[iteratorSymbol]) {
+        size = symbolEach(collection, iterator, createCallback);
+        size && size === completed && callback(null, result);
+      } else if (typeof collection === obj) {
+        keys = nativeKeys(collection);
+        size = keys.length;
+        baseEach(collection, iterator, createCallback, keys);
+      }
+      if (!size) {
+        return callback(null, {});
+      }
+
+      function createCallback(key, value) {
+        return function done(err, res) {
+          if (key === null) {
+            throwError();
+          }
+          if (err) {
+            key = null;
+            callback = once(callback);
+            callback(err, objectClone(result));
+            return;
+          }
+          if (!!res === bool) {
+            result[key] = value;
+          }
+          key = null;
+          if (++completed === size) {
+            callback(null, result);
+          }
+        };
+      }
+    };
+  }
+
+  /**
+   * @private
+   * @param {boolean} bool
+   */
+  function createPickSeries(bool) {
+    return function(collection, iterator, callback) {
+      callback = onlyOnce(callback || noop);
+      var size, key, value, keys, iter, item, iterate;
+      var sync = false;
+      var result = {};
+      var completed = 0;
+
+      if (isArray(collection)) {
+        size = collection.length;
+        iterate = iterator.length === 3 ? arrayIteratorWithIndex : arrayIterator;
+      } else if (!collection) {
+      } else if (iteratorSymbol && collection[iteratorSymbol]) {
+        size = Infinity;
+        iter = collection[iteratorSymbol]();
+        iterate = iterator.length === 3 ? symbolIteratorWithKey : symbolIterator;
+      } else if (typeof collection === obj) {
+        keys = nativeKeys(collection);
+        size = keys.length;
+        iterate = iterator.length === 3 ? objectIteratorWithKey : objectIterator;
+      }
+      if (!size) {
+        return callback(null, {});
+      }
+      iterate();
+
+      function arrayIterator() {
+        key = completed;
+        value = collection[completed];
+        iterator(value, done);
+      }
+
+      function arrayIteratorWithIndex() {
+        key = completed;
+        value = collection[completed];
+        iterator(value, completed, done);
+      }
+
+      function symbolIterator() {
+        key = completed;
+        item = iter.next();
+        value = item.value;
+        item.done ? callback(null, result) : iterator(value, done);
+      }
+
+      function symbolIteratorWithKey() {
+        key = completed;
+        item = iter.next();
+        value = item.value;
+        item.done ? callback(null, result) : iterator(value, key, done);
+      }
+
+      function objectIterator() {
+        key = keys[completed];
+        value = collection[key];
+        iterator(value, done);
+      }
+
+      function objectIteratorWithKey() {
+        key = keys[completed];
+        value = collection[key];
+        iterator(value, key, done);
+      }
+
+      function done(err, res) {
+        if (err) {
+          callback(err, result);
+          return;
+        }
+        if (!!res === bool) {
+          result[key] = value;
+        }
+        if (++completed === size) {
+          iterate = throwError;
+          callback(null, result);
+        } else if (sync) {
+          nextTick(iterate);
+        } else {
+          sync = true;
+          iterate();
+        }
+        sync = false;
+      }
+    };
+  }
+
+  /**
+   * @private
+   * @param {boolean} bool
+   */
+  function createPickLimit(bool) {
+    return function(collection, limit, iterator, callback) {
+      callback = callback || noop;
+      var size, index, key, value, keys, iter, item, iterate;
+      var sync = false;
+      var result = {};
+      var started = 0;
+      var completed = 0;
+
+      if (isArray(collection)) {
+        size = collection.length;
+        iterate = iterator.length === 3 ? arrayIteratorWithIndex : arrayIterator;
+      } else if (!collection) {
+      } else if (iteratorSymbol && collection[iteratorSymbol]) {
+        size = Infinity;
+        iter = collection[iteratorSymbol]();
+        iterate = iterator.length === 3 ? symbolIteratorWithKey : symbolIterator;
+      } else if (typeof collection === obj) {
+        keys = nativeKeys(collection);
+        size = keys.length;
+        iterate = iterator.length === 3 ? objectIteratorWithKey : objectIterator;
+      }
+      if (!size || isNaN(limit) || limit < 1) {
+        return callback(null, {});
+      }
+      timesSync(limit > size ? size : limit, iterate);
+
+      function arrayIterator() {
+        index = started++;
+        if (index < size) {
+          value = collection[index];
+          iterator(value, createCallback(value, index));
+        }
+      }
+
+      function arrayIteratorWithIndex() {
+        index = started++;
+        if (index < size) {
+          value = collection[index];
+          iterator(value, index, createCallback(value, index));
+        }
+      }
+
+      function symbolIterator() {
+        item = iter.next();
+        if (item.done === false) {
+          value = item.value;
+          iterator(value, createCallback(value, started++));
+        } else if (completed === started && iterator !== noop) {
+          iterator = noop;
+          callback(null, result);
+        }
+      }
+
+      function symbolIteratorWithKey() {
+        item = iter.next();
+        if (item.done === false) {
+          value = item.value;
+          iterator(value, started, createCallback(value, started++));
+        } else if (completed === started && iterator !== noop) {
+          iterator = noop;
+          callback(null, result);
+        }
+      }
+
+      function objectIterator() {
+        if (started < size) {
+          key = keys[started++];
+          value = collection[key];
+          iterator(value, createCallback(value, key));
+        }
+      }
+
+      function objectIteratorWithKey() {
+        if (started < size) {
+          key = keys[started++];
+          value = collection[key];
+          iterator(value, key, createCallback(value, key));
+        }
+      }
+
+      function createCallback(value, key) {
+        return function(err, res) {
+          if (key === null) {
+            throwError();
+          }
+          if (err) {
+            key = null;
+            iterate = noop;
+            callback = once(callback);
+            callback(err, objectClone(result));
+            return;
+          }
+          if (!!res === bool) {
+            result[key] = value;
+          }
+          key = null;
+          if (++completed === size) {
+            iterate = throwError;
+            callback = onlyOnce(callback);
+            callback(null, result);
+          } else if (sync) {
+            nextTick(iterate);
+          } else {
+            sync = true;
+            iterate();
+          }
+          sync = false;
+        };
+      }
+    };
+  }
+
+  /**
+   * @memberof async
+   * @namespace reduce
+   * @param {Array|Object} collection
+   * @param {*} result
+   * @param {Function} iterator
+   * @param {Function} callback
+   * @example
+   *
+   * // array
+   * var order = [];
+   * var collection = [1, 3, 2, 4];
+   * var iterator = function(result, num, done) {
+   *   setTimeout(function() {
+   *     order.push(num);
+   *     done(null, result + num);
+   *   }, num * 10);
+   * };
+   * async.reduce(collection, 0, iterator, function(err, res) {
+   *   console.log(res); // 10
+   *   console.log(order); // [1, 3, 2, 4]
+   * });
+   *
+   * @example
+   *
+   * // array with index
+   * var order = [];
+   * var collection = [1, 3, 2, 4];
+   * var iterator = function(result, num, index, done) {
+   *   setTimeout(function() {
+   *     order.push([num, index]);
+   *     done(null, result + num);
+   *   }, num * 10);
+   * };
+   * async.reduce(collection, '', iterator, function(err, res) {
+   *   console.log(res); // '1324'
+   *   console.log(order); // [[1, 0], [3, 1], [2, 2], [4, 3]]
+   * });
+   *
+   * @example
+   *
+   * // object
+   * var order = [];
+   * var object = { a: 1, b: 3, c: 2, d: 4 };
+   * var iterator = function(result, num, done) {
+   *   setTimeout(function() {
+   *     order.push(num);
+   *     done(null, result + num);
+   *   }, num * 10);
+   * };
+   * async.reduce(collection, '', iterator, function(err, res) {
+   *   console.log(res); // '1324'
+   *   console.log(order); // [1, 3, 2, 4]
+   * });
+   *
+   * @example
+   *
+   * // object with key
+   * var order = [];
+   * var object = { a: 1, b: 3, c: 2, d: 4 };
+   * var iterator = function(result, num, key, done) {
+   *   setTimeout(function() {
+   *     order.push([num, key]);
+   *     done(null, result + num);
+   *   }, num * 10);
+   * };
+   * async.reduce(collection, 0, iterator, function(err, res) {
+   *   console.log(res); // 10
+   *   console.log(order); // [[1, 'a'], [3, 'b'], [2, 'b'], [4, 'd']]
+   * });
+   *
+   */
+  function reduce(collection, result, iterator, callback) {
+    callback = onlyOnce(callback || noop);
+    var size, key, keys, iter, item, iterate;
+    var sync = false;
+    var completed = 0;
+
+    if (isArray(collection)) {
+      size = collection.length;
+      iterate = iterator.length === 4 ? arrayIteratorWithIndex : arrayIterator;
+    } else if (!collection) {
+    } else if (iteratorSymbol && collection[iteratorSymbol]) {
+      size = Infinity;
+      iter = collection[iteratorSymbol]();
+      iterate = iterator.length === 4 ? symbolIteratorWithKey : symbolIterator;
+    } else if (typeof collection === obj) {
+      keys = nativeKeys(collection);
+      size = keys.length;
+      iterate = iterator.length === 4 ? objectIteratorWithKey : objectIterator;
+    }
+    if (!size) {
+      return callback(null, result);
+    }
+    iterate(result);
+
+    function arrayIterator(result) {
+      iterator(result, collection[completed], done);
+    }
+
+    function arrayIteratorWithIndex(result) {
+      iterator(result, collection[completed], completed, done);
+    }
+
+    function symbolIterator(result) {
+      item = iter.next();
+      item.done ? callback(null, result) : iterator(result, item.value, done);
+    }
+
+    function symbolIteratorWithKey(result) {
+      item = iter.next();
+      item.done ? callback(null, result) : iterator(result, item.value, completed, done);
+    }
+
+    function objectIterator(result) {
+      iterator(result, collection[keys[completed]], done);
+    }
+
+    function objectIteratorWithKey(result) {
+      key = keys[completed];
+      iterator(result, collection[key], key, done);
+    }
+
+    function done(err, result) {
+      if (err) {
+        callback(err, result);
+      } else if (++completed === size) {
+        iterator = throwError;
+        callback(null, result);
+      } else if (sync) {
+        nextTick(function() {
+          iterate(result);
+        });
+      } else {
+        sync = true;
+        iterate(result);
+      }
+      sync = false;
+    }
+  }
+
+  /**
+   * @memberof async
+   * @namespace reduceRight
+   * @param {Array|Object} collection
+   * @param {*} result
+   * @param {Function} iterator
+   * @param {Function} callback
+   * @example
+   *
+   * // array
+   * var order = [];
+   * var collection = [1, 3, 2, 4];
+   * var iterator = function(result, num, done) {
+   *   setTimeout(function() {
+   *     order.push(num);
+   *     done(null, result + num);
+   *   }, num * 10);
+   * };
+   * async.reduceRight(collection, 0, iterator, function(err, res) {
+   *   console.log(res); // 10
+   *   console.log(order); // [4, 2, 3, 1]
+   * });
+   *
+   * @example
+   *
+   * // array with index
+   * var order = [];
+   * var collection = [1, 3, 2, 4];
+   * var iterator = function(result, num, index, done) {
+   *   setTimeout(function() {
+   *     order.push([num, index]);
+   *     done(null, result + num);
+   *   }, num * 10);
+   * };
+   * async.reduceRight(collection, '', iterator, function(err, res) {
+   *   console.log(res); // '4231'
+   *   console.log(order); // [[4, 3], [2, 2], [3, 1], [1, 0]]
+   * });
+   *
+   * @example
+   *
+   * // object
+   * var order = [];
+   * var object = { a: 1, b: 3, c: 2, d: 4 };
+   * var iterator = function(result, num, done) {
+   *   setTimeout(function() {
+   *     order.push(num);
+   *     done(null, result + num);
+   *   }, num * 10);
+   * };
+   * async.reduceRight(collection, '', iterator, function(err, res) {
+   *   console.log(res); // '4231'
+   *   console.log(order); // [4, 2, 3, 1]
+   * });
+   *
+   * @example
+   *
+   * // object with key
+   * var order = [];
+   * var object = { a: 1, b: 3, c: 2, d: 4 };
+   * var iterator = function(result, num, key, done) {
+   *   setTimeout(function() {
+   *     order.push([num, key]);
+   *     done(null, result + num);
+   *   }, num * 10);
+   * };
+   * async.reduceRight(collection, 0, iterator, function(err, res) {
+   *   console.log(res); // 10
+   *   console.log(order); // [[4, 3], [2, 2], [3, 1], [1, 0]]
+   * });
+   *
+   */
+  function reduceRight(collection, result, iterator, callback) {
+    callback = onlyOnce(callback || noop);
+    var resIndex, index, key, keys, iter, item, col, iterate;
+    var sync = false;
+
+    if (isArray(collection)) {
+      resIndex = collection.length;
+      iterate = iterator.length === 4 ? arrayIteratorWithIndex : arrayIterator;
+    } else if (!collection) {
+    } else if (iteratorSymbol && collection[iteratorSymbol]) {
+      col = [];
+      iter = collection[iteratorSymbol]();
+      index = -1;
+      while ((item = iter.next()).done === false) {
+        col[++index] = item.value;
+      }
+      collection = col;
+      resIndex = col.length;
+      iterate = iterator.length === 4 ? arrayIteratorWithIndex : arrayIterator;
+    } else if (typeof collection === obj) {
+      keys = nativeKeys(collection);
+      resIndex = keys.length;
+      iterate = iterator.length === 4 ? objectIteratorWithKey : objectIterator;
+    }
+    if (!resIndex) {
+      return callback(null, result);
+    }
+    iterate(result);
+
+    function arrayIterator(result) {
+      iterator(result, collection[--resIndex], done);
+    }
+
+    function arrayIteratorWithIndex(result) {
+      iterator(result, collection[--resIndex], resIndex, done);
+    }
+
+    function objectIterator(result) {
+      iterator(result, collection[keys[--resIndex]], done);
+    }
+
+    function objectIteratorWithKey(result) {
+      key = keys[--resIndex];
+      iterator(result, collection[key], key, done);
+    }
+
+    function done(err, result) {
+      if (err) {
+        callback(err, result);
+      } else if (resIndex === 0) {
+        iterate = throwError;
+        callback(null, result);
+      } else if (sync) {
+        nextTick(function() {
+          iterate(result);
+        });
+      } else {
+        sync = true;
+        iterate(result);
+      }
+      sync = false;
+    }
+  }
+
+  /**
+   * @private
+   * @param {Function} arrayEach
+   * @param {Function} baseEach
+   * @param {Function} symbolEach
+   */
+  function createTransform(arrayEach, baseEach, symbolEach) {
+    return function transform(collection, accumulator, iterator, callback) {
+      if (arguments.length === 3) {
+        callback = iterator;
+        iterator = accumulator;
+        accumulator = undefined;
+      }
+      callback = callback || noop;
+      var size, keys, result;
+      var completed = 0;
+
+      if (isArray(collection)) {
+        size = collection.length;
+        result = accumulator !== undefined ? accumulator : [];
+        arrayEach(collection, result, iterator, done);
+      } else if (!collection) {
+      } else if (iteratorSymbol && collection[iteratorSymbol]) {
+        result = accumulator !== undefined ? accumulator : {};
+        size = symbolEach(collection, result, iterator, done);
+        size && size === completed && callback(null, result);
+      } else if (typeof collection === obj) {
+        keys = nativeKeys(collection);
+        size = keys.length;
+        result = accumulator !== undefined ? accumulator : {};
+        baseEach(collection, result, iterator, done, keys);
+      }
+      if (!size) {
+        callback(null, accumulator !== undefined ? accumulator : result || {});
+      }
+
+      function done(err, bool) {
+        if (err) {
+          callback = once(callback);
+          callback(err, isArray(result) ? createArray(result) : objectClone(result));
+        } else if (++completed === size) {
+          callback(null, result);
+        } else if (bool === false) {
+          callback = once(callback);
+          callback(null, isArray(result) ? createArray(result) : objectClone(result));
+        }
+      }
+    };
+  }
+
+  /**
+   * @memberof async
+   * @namespace transformSeries
+   * @param {Array|Object} collection
+   * @param {Array|Object|Function} [accumulator]
+   * @param {Function} [iterator]
+   * @param {Function} [callback]
+   * @example
+   *
+   * // array
+   * var order = [];
+   * var collection = [1, 3, 2, 4];
+   * var iterator = function(result, num, done) {
+   *   setTimeout(function() {
+   *     order.push(num);
+   *     result.push(num)
+   *     done();
+   *   }, num * 10);
+   * };
+   * async.transformSeries(collection, iterator, function(err, res) {
+   *   console.log(res); // [1, 3, 2, 4]
+   *   console.log(order); // [1, 3, 2, 4]
+   * });
+   *
+   * @example
+   *
+   * // array with index and accumulator
+   * var order = [];
+   * var collection = [1, 3, 2, 4];
+   * var iterator = function(result, num, index, done) {
+   *   setTimeout(function() {
+   *     order.push([num, index]);
+   *     result[index] = num;
+   *     done();
+   *   }, num * 10);
+   * };
+   * async.transformSeries(collection, {}, iterator, function(err, res) {
+   *   console.log(res); // { '0': 1, '1': 3, '2': 2, '3': 4 }
+   *   console.log(order); // [[1, 0], [3, 1], [2, 2], [4, 3]]
+   * });
+   *
+   * @example
+   *
+   * // object with accumulator
+   * var order = [];
+   * var object = { a: 1, b: 3, c: 2, d: 4 };
+   * var iterator = function(result, num, done) {
+   *   setTimeout(function() {
+   *     order.push(num);
+   *     result.push(num);
+   *     done();
+   *   }, num * 10);
+   * };
+   * async.transformSeries(collection, [], iterator, function(err, res) {
+   *   console.log(res); // [1, 3, 2, 4]
+   *   console.log(order); // [1, 3, 2, 4]
+   * });
+   *
+   * @example
+   *
+   * // object with key
+   * var order = [];
+   * var object = { a: 1, b: 3, c: 2, d: 4 };
+   * var iterator = function(result, num, key, done) {
+   *   setTimeout(function() {
+   *     order.push([num, key]);
+   *     result[key] = num;
+   *     done();
+   *   }, num * 10);
+   * };
+   * async.transformSeries(collection, iterator, function(err, res) {
+   *   console.log(res); //  { a: 1, b: 3, c: 2, d: 4 }
+   *   console.log(order); // [[1, 'a'], [3, 'b'], [2, 'b'], [4, 'd']]
+   * });
+   *
+   */
+  function transformSeries(collection, accumulator, iterator, callback) {
+    if (arguments.length === 3) {
+      callback = iterator;
+      iterator = accumulator;
+      accumulator = undefined;
+    }
+    callback = onlyOnce(callback || noop);
+    var size, key, keys, iter, item, iterate, result;
+    var sync = false;
+    var completed = 0;
+
+    if (isArray(collection)) {
+      size = collection.length;
+      result = accumulator !== undefined ? accumulator : [];
+      iterate = iterator.length === 4 ? arrayIteratorWithIndex : arrayIterator;
+    } else if (!collection) {
+    } else if (iteratorSymbol && collection[iteratorSymbol]) {
+      size = Infinity;
+      iter = collection[iteratorSymbol]();
+      result = accumulator !== undefined ? accumulator : {};
+      iterate = iterator.length === 4 ? symbolIteratorWithKey : symbolIterator;
+    } else if (typeof collection === obj) {
+      keys = nativeKeys(collection);
+      size = keys.length;
+      result = accumulator !== undefined ? accumulator : {};
+      iterate = iterator.length === 4 ? objectIteratorWithKey : objectIterator;
+    }
+    if (!size) {
+      return callback(null, accumulator !== undefined ? accumulator : result || {});
+    }
+    iterate();
+
+    function arrayIterator() {
+      iterator(result, collection[completed], done);
+    }
+
+    function arrayIteratorWithIndex() {
+      iterator(result, collection[completed], completed, done);
+    }
+
+    function symbolIterator() {
+      item = iter.next();
+      item.done ? callback(null, result) : iterator(result, item.value, done);
+    }
+
+    function symbolIteratorWithKey() {
+      item = iter.next();
+      item.done ? callback(null, result) : iterator(result, item.value, completed, done);
+    }
+
+    function objectIterator() {
+      iterator(result, collection[keys[completed]], done);
+    }
+
+    function objectIteratorWithKey() {
+      key = keys[completed];
+      iterator(result, collection[key], key, done);
+    }
+
+    function done(err, bool) {
+      if (err) {
+        callback(err, result);
+      } else if (++completed === size || bool === false) {
+        iterate = throwError;
+        callback(null, result);
+      } else if (sync) {
+        nextTick(iterate);
+      } else {
+        sync = true;
+        iterate();
+      }
+      sync = false;
+    }
+  }
+
+  /**
+   * @memberof async
+   * @namespace transformLimit
+   * @param {Array|Object} collection
+   * @param {number} limit - limit >= 1
+   * @param {Array|Object|Function} [accumulator]
+   * @param {Function} [iterator]
+   * @param {Function} [callback]
+   * @example
+   *
+   * // array
+   * var order = [];
+   * var array = [1, 5, 3, 4, 2];
+   * var iterator = function(result, num, done) {
+   *   setTimeout(function() {
+   *     order.push(num);
+   *     result.push(num);
+   *     done();
+   *   }, num * 10);
+   * };
+   * async.transformLimit(array, 2, iterator, function(err, res) {
+   *   console.log(res); // [1, 3, 5, 2, 4]
+   *   console.log(order); // [1, 3, 5, 2, 4]
+   * });
+   *
+   * @example
+   *
+   * // array with index and accumulator
+   * var order = [];
+   * var array = [1, 5, 3, 4, 2];
+   * var iterator = function(result, num, index, done) {
+   *   setTimeout(function() {
+   *     order.push([num, index]);
+   *     result[index] = key;
+   *     done();
+   *   }, num * 10);
+   * };
+   * async.transformLimit(array, 2, {}, iterator, function(err, res) {
+   *   console.log(res); // { '0': 1, '1': 5, '2': 3, '3': 4, '4': 2 }
+   *   console.log(order); // [[1, 0], [3, 2], [5, 1], [2, 4], [4, 3]]
+   * });
+   *
+   * @example
+   *
+   * // object with accumulator
+   * var order = [];
+   * var object = { a: 1, b: 5, c: 3, d: 4, e: 2 };
+   * var iterator = function(result, num, done) {
+   *   setTimeout(function() {
+   *     order.push(num);
+   *     result.push(num);
+   *     done();
+   *   }, num * 10);
+   * };
+   * async.transformLimit(object, 2, [], iterator, function(err, res) {
+   *   console.log(res); // [1, 3, 5, 2, 4]
+   *   console.log(order); // [1, 3, 5, 2, 4]
+   * });
+   *
+   * @example
+   *
+   * // object with key
+   * var order = [];
+   * var object = { a: 1, b: 5, c: 3, d: 4, e: 2 };
+   * var iterator = function(result, num, key, done) {
+   *   setTimeout(function() {
+   *     order.push([num, key]);
+   *     result[key] = num;
+   *     done();
+   *   }, num * 10);
+   * };
+   * async.transformLimit(object, 2, iterator, function(err, res) {
+   *   console.log(res); // { a: 1, b: 5, c: 3, d: 4, e: 2 };
+   *   console.log(order); // [[1, 'a'], [3, 'c'], [5, 'b'], [2, 'e'], [4, 'd']]
+   * });
+   *
+   */
+  function transformLimit(collection, limit, accumulator, iterator, callback) {
+    if (arguments.length === 4) {
+      callback = iterator;
+      iterator = accumulator;
+      accumulator = undefined;
+    }
+    callback = callback || noop;
+    var size, index, key, keys, iter, item, iterate, result;
+    var sync = false;
+    var started = 0;
+    var completed = 0;
+
+    if (isArray(collection)) {
+      size = collection.length;
+      result = accumulator !== undefined ? accumulator : [];
+      iterate = iterator.length === 4 ? arrayIteratorWithIndex : arrayIterator;
+    } else if (!collection) {
+    } else if (iteratorSymbol && collection[iteratorSymbol]) {
+      size = Infinity;
+      iter = collection[iteratorSymbol]();
+      result = accumulator !== undefined ? accumulator : {};
+      iterate = iterator.length === 4 ? symbolIteratorWithKey : symbolIterator;
+    } else if (typeof collection === obj) {
+      keys = nativeKeys(collection);
+      size = keys.length;
+      result = accumulator !== undefined ? accumulator : {};
+      iterate = iterator.length === 4 ? objectIteratorWithKey : objectIterator;
+    }
+    if (!size || isNaN(limit) || limit < 1) {
+      return callback(null, accumulator !== undefined ? accumulator : result || {});
+    }
+    timesSync(limit > size ? size : limit, iterate);
+
+    function arrayIterator() {
+      index = started++;
+      if (index < size) {
+        iterator(result, collection[index], onlyOnce(done));
+      }
+    }
+
+    function arrayIteratorWithIndex() {
+      index = started++;
+      if (index < size) {
+        iterator(result, collection[index], index, onlyOnce(done));
+      }
+    }
+
+    function symbolIterator() {
+      item = iter.next();
+      if (item.done === false) {
+        started++;
+        iterator(result, item.value, onlyOnce(done));
+      } else if (completed === started && iterator !== noop) {
+        iterator = noop;
+        callback(null, result);
+      }
+    }
+
+    function symbolIteratorWithKey() {
+      item = iter.next();
+      if (item.done === false) {
+        iterator(result, item.value, started++, onlyOnce(done));
+      } else if (completed === started && iterator !== noop) {
+        iterator = noop;
+        callback(null, result);
+      }
+    }
+
+    function objectIterator() {
+      index = started++;
+      if (index < size) {
+        iterator(result, collection[keys[index]], onlyOnce(done));
+      }
+    }
+
+    function objectIteratorWithKey() {
+      index = started++;
+      if (index < size) {
+        key = keys[index];
+        iterator(result, collection[key], key, onlyOnce(done));
+      }
+    }
+
+    function done(err, bool) {
+      if (err || bool === false) {
+        iterate = noop;
+        callback(err || null, isArray(result) ? createArray(result) : objectClone(result));
+        callback = noop;
+      } else if (++completed === size) {
+        iterator = noop;
+        callback(null, result);
+      } else if (sync) {
+        nextTick(iterate);
+      } else {
+        sync = true;
+        iterate();
+      }
+      sync = false;
+    }
+  }
+
+  /**
+   * @private
+   * @param {function} arrayEach
+   * @param {function} baseEach
+   * @param {function} symbolEach
+   */
+  function createSortBy(arrayEach, baseEach, symbolEach) {
+    return function sortBy(collection, iterator, callback) {
+      callback = callback || noop;
+      var size, array, criteria;
+      var completed = 0;
+
+      if (isArray(collection)) {
+        size = collection.length;
+        array = Array(size);
+        criteria = Array(size);
+        arrayEach(collection, iterator, createCallback);
+      } else if (!collection) {
+      } else if (iteratorSymbol && collection[iteratorSymbol]) {
+        array = [];
+        criteria = [];
+        size = symbolEach(collection, iterator, createCallback);
+        size && size === completed && callback(null, sortByCriteria(array, criteria));
+      } else if (typeof collection === obj) {
+        var keys = nativeKeys(collection);
+        size = keys.length;
+        array = Array(size);
+        criteria = Array(size);
+        baseEach(collection, iterator, createCallback, keys);
+      }
+      if (!size) {
+        callback(null, []);
+      }
+
+      function createCallback(index, value) {
+        var called = false;
+        array[index] = value;
+        return function done(err, criterion) {
+          if (called) {
+            throwError();
+          }
+          called = true;
+          criteria[index] = criterion;
+          if (err) {
+            callback = once(callback);
+            callback(err);
+          } else if (++completed === size) {
+            callback(null, sortByCriteria(array, criteria));
+          }
+        };
+      }
+    };
+  }
+
+  /**
+   * @memberof async
+   * @namespace sortBySeries
+   * @param {Array|Object} collection
+   * @param {Function} iterator
+   * @param {Function} callback
+   * @example
+   *
+   * // array
+   * var order = [];
+   * var array = [1, 3, 2];
+   * var iterator = function(num, done) {
+   *   setTimeout(function() {
+   *     order.push(num);
+   *     done(null, num);
+   *   }, num * 10);
+   * };
+   * async.sortBySeries(array, iterator, function(err, res) {
+   *   console.log(res); // [1, 2, 3];
+   *   console.log(order); // [1, 3, 2]
+   * });
+   *
+   * @example
+   *
+   * // array with index
+   * var order = [];
+   * var array = [1, 3, 2];
+   * var iterator = function(num, index, done) {
+   *   setTimeout(function() {
+   *     order.push([num, index]);
+   *     done(null, num);
+   *   }, num * 10);
+   * };
+   * async.sortBySeries(array, iterator, function(err, res) {
+   *   console.log(res); // [1, 2, 3]
+   *   console.log(order); // [[1, 0], [3, 1], [2, 2]]
+   * });
+   *
+   * @example
+   *
+   * // object
+   * var order = [];
+   * var object = { a: 1, b: 3, c: 2 };
+   * var iterator = function(num, done) {
+   *   setTimeout(function() {
+   *     order.push(num);
+   *     done(null, num);
+   *   }, num * 10);
+   * };
+   * async.sortBySeries(object, iterator, function(err, res) {
+   *   console.log(res); // [1, 2, 3]
+   *   console.log(order); // [1, 3, 2]
+   * });
+   *
+   * @example
+   *
+   * // object with key
+   * var order = [];
+   * var object = { a: 1, b: 3, c: 2 };
+   * var iterator = function(num, key, done) {
+   *   setTimeout(function() {
+   *     order.push([num, key]);
+   *     done(null, num);
+   *   }, num * 10);
+   * };
+   * async.sortBySeries(object, iterator, function(err, res) {
+   *   console.log(res); // [1, 2, 3]
+   *   console.log(order); // [[1, 'a'], [3, 'b'], [2, 'c']]
+   * });
+   *
+   */
+  function sortBySeries(collection, iterator, callback) {
+    callback = onlyOnce(callback || noop);
+    var size, key, value, keys, iter, item, array, criteria, iterate;
+    var sync = false;
+    var completed = 0;
+
+    if (isArray(collection)) {
+      size = collection.length;
+      array = collection;
+      criteria = Array(size);
+      iterate = iterator.length === 3 ? arrayIteratorWithIndex : arrayIterator;
+    } else if (!collection) {
+    } else if (iteratorSymbol && collection[iteratorSymbol]) {
+      size = Infinity;
+      array = [];
+      criteria = [];
+      iter = collection[iteratorSymbol]();
+      iterate = iterator.length === 3 ? symbolIteratorWithKey : symbolIterator;
+    } else if (typeof collection === obj) {
+      keys = nativeKeys(collection);
+      size = keys.length;
+      array = Array(size);
+      criteria = Array(size);
+      iterate = iterator.length === 3 ? objectIteratorWithKey : objectIterator;
+    }
+    if (!size) {
+      return callback(null, []);
+    }
+    iterate();
+
+    function arrayIterator() {
+      value = collection[completed];
+      iterator(value, done);
+    }
+
+    function arrayIteratorWithIndex() {
+      value = collection[completed];
+      iterator(value, completed, done);
+    }
+
+    function symbolIterator() {
+      item = iter.next();
+      if (item.done) {
+        return callback(null, sortByCriteria(array, criteria));
+      }
+      value = item.value;
+      array[completed] = value;
+      iterator(value, done);
+    }
+
+    function symbolIteratorWithKey() {
+      item = iter.next();
+      if (item.done) {
+        return callback(null, sortByCriteria(array, criteria));
+      }
+      value = item.value;
+      array[completed] = value;
+      iterator(value, completed, done);
+    }
+
+    function objectIterator() {
+      value = collection[keys[completed]];
+      array[completed] = value;
+      iterator(value, done);
+    }
+
+    function objectIteratorWithKey() {
+      key = keys[completed];
+      value = collection[key];
+      array[completed] = value;
+      iterator(value, key, done);
+    }
+
+    function done(err, criterion) {
+      criteria[completed] = criterion;
+      if (err) {
+        callback(err);
+      } else if (++completed === size) {
+        iterate = throwError;
+        callback(null, sortByCriteria(array, criteria));
+      } else if (sync) {
+        nextTick(iterate);
+      } else {
+        sync = true;
+        iterate();
+      }
+      sync = false;
+    }
+  }
+
+  /**
+   * @memberof async
+   * @namespace sortByLimit
+   * @param {Array|Object} collection
+   * @param {number} limit - limit >= 1
+   * @param {Function} iterator
+   * @param {Function} callback
+   * @example
+   *
+   * // array
+   * var order = [];
+   * var array = [1, 5, 3, 4, 2];
+   * var iterator = function(num, done) {
+   *   setTimeout(function() {
+   *     order.push(num);
+   *     done(null, num);
+   *   }, num * 10);
+   * };
+   * async.sortByLimit(array, 2, iterator, function(err, res) {
+   *   console.log(res); // [1, 2, 3, 4, 5]
+   *   console.log(order); // [1, 3, 5, 2, 4]
+   * });
+   *
+   * @example
+   *
+   * // array with index
+   * var order = [];
+   * var array = [1, 5, 3, 4, 2];
+   * var iterator = function(num, index, done) {
+   *   setTimeout(function() {
+   *     order.push([num, index]);
+   *     done(null, num);
+   *   }, num * 10);
+   * };
+   * async.sortByLimit(array, 2, iterator, function(err, res) {
+   *   console.log(res); // [1, 2, 3, 4, 5]
+   *   console.log(order); // [[1, 0], [3, 2], [5, 1], [2, 4], [4, 3]]
+   * });
+   *
+   * @example
+   *
+   * // object
+   * var order = [];
+   * var object = { a: 1, b: 5, c: 3, d: 4, e: 2 };
+   * var iterator = function(num, done) {
+   *   setTimeout(function() {
+   *     order.push(num);
+   *     done(null, num);
+   *   }, num * 10);
+   * };
+   * async.sortByLimit(object, 2, iterator, function(err, res) {
+   *   console.log(res); // [1, 2, 3, 4, 5]
+   *   console.log(order); // [1, 3, 5, 2, 4]
+   * });
+   *
+   * @example
+   *
+   * // object with key
+   * var order = [];
+   * var object = { a: 1, b: 5, c: 3, d: 4, e: 2 };
+   * var iterator = function(num, key, done) {
+   *   setTimeout(function() {
+   *     order.push([num, key]);
+   *     done(null, num);
+   *   }, num * 10);
+   * };
+   * async.sortByLimit(object, 2, iterator, function(err, res) {
+   *   console.log(res); // [1, 2, 3, 4, 5]
+   *   console.log(order); // [[1, 'a'], [3, 'c'], [5, 'b'], [2, 'e'], [4, 'd']]
+   * });
+   *
+   */
+  function sortByLimit(collection, limit, iterator, callback) {
+    callback = callback || noop;
+    var size, index, key, value, array, keys, iter, item, criteria, iterate;
+    var sync = false;
+    var started = 0;
+    var completed = 0;
+
+    if (isArray(collection)) {
+      size = collection.length;
+      array = collection;
+      iterate = iterator.length === 3 ? arrayIteratorWithIndex : arrayIterator;
+    } else if (!collection) {
+    } else if (iteratorSymbol && collection[iteratorSymbol]) {
+      size = Infinity;
+      iter = collection[iteratorSymbol]();
+      array = [];
+      criteria = [];
+      iterate = iterator.length === 3 ? symbolIteratorWithKey : symbolIterator;
+    } else if (typeof collection === obj) {
+      keys = nativeKeys(collection);
+      size = keys.length;
+      array = Array(size);
+      iterate = iterator.length === 3 ? objectIteratorWithKey : objectIterator;
+    }
+    if (!size || isNaN(limit) || limit < 1) {
+      return callback(null, []);
+    }
+    criteria = criteria || Array(size);
+    timesSync(limit > size ? size : limit, iterate);
+
+    function arrayIterator() {
+      if (started < size) {
+        value = collection[started];
+        iterator(value, createCallback(value, started++));
+      }
+    }
+
+    function arrayIteratorWithIndex() {
+      index = started++;
+      if (index < size) {
+        value = collection[index];
+        iterator(value, index, createCallback(value, index));
+      }
+    }
+
+    function symbolIterator() {
+      item = iter.next();
+      if (item.done === false) {
+        value = item.value;
+        array[started] = value;
+        iterator(value, createCallback(value, started++));
+      } else if (completed === started && iterator !== noop) {
+        iterator = noop;
+        callback(null, sortByCriteria(array, criteria));
+      }
+    }
+
+    function symbolIteratorWithKey() {
+      item = iter.next();
+      if (item.done === false) {
+        value = item.value;
+        array[started] = value;
+        iterator(value, started, createCallback(value, started++));
+      } else if (completed === started && iterator !== noop) {
+        iterator = noop;
+        callback(null, sortByCriteria(array, criteria));
+      }
+    }
+
+    function objectIterator() {
+      if (started < size) {
+        value = collection[keys[started]];
+        array[started] = value;
+        iterator(value, createCallback(value, started++));
+      }
+    }
+
+    function objectIteratorWithKey() {
+      if (started < size) {
+        key = keys[started];
+        value = collection[key];
+        array[started] = value;
+        iterator(value, key, createCallback(value, started++));
+      }
+    }
+
+    function createCallback(value, index) {
+      var called = false;
+      return function(err, criterion) {
+        if (called) {
+          throwError();
+        }
+        called = true;
+        criteria[index] = criterion;
+        if (err) {
+          iterate = noop;
+          callback(err);
+          callback = noop;
+        } else if (++completed === size) {
+          callback(null, sortByCriteria(array, criteria));
+        } else if (sync) {
+          nextTick(iterate);
+        } else {
+          sync = true;
+          iterate();
+        }
+        sync = false;
+      };
+    }
+  }
+
+  /**
+   * @memberof async
+   * @namespace some
+   * @param {Array|Object} collection
+   * @param {Function} iterator
+   * @param {Function} callback
+   * @example
+   *
+   * // array
+   * var order = [];
+   * var array = [1, 3, 2];
+   * var iterator = function(num, done) {
+   *   setTimeout(function() {
+   *     order.push(num);
+   *     done(null, num % 2);
+   *   }, num * 10);
+   * };
+   * async.some(array, iterator, function(err, res) {
+   *   console.log(res); // true
+   *   console.log(order); // [1]
+   * });
+   *
+   * @example
+   *
+   * // array with index
+   * var order = [];
+   * var array = [1, 3, 2];
+   * var iterator = function(num, index, done) {
+   *   setTimeout(function() {
+   *     order.push([num, index]);
+   *     done(null, num % 2);
+   *   }, num * 10);
+   * };
+   * async.some(array, iterator, function(err, res) {
+   *   console.log(res); // true
+   *   console.log(order); // [[1, 0]]
+   * });
+   *
+   * @example
+   *
+   * // object
+   * var order = [];
+   * var object = { a: 1, b: 3, c: 2 };
+   * var iterator = function(num, done) {
+   *   setTimeout(function() {
+   *     order.push(num);
+   *     done(null, num % 2);
+   *   }, num * 10);
+   * };
+   * async.some(object, iterator, function(err, res) {
+   *   console.log(res); // true
+   *   console.log(order); // [1]
+   * });
+   *
+   * @example
+   *
+   * // object with key
+   * var order = [];
+   * var object = { a: 1, b: 3, c: 2 };
+   * var iterator = function(num, key, done) {
+   *   setTimeout(function() {
+   *     order.push([num, key]);
+   *     done(null, num % 2);
+   *   }, num * 10);
+   * };
+   * async.some(object, iterator, function(err, res) {
+   *   console.log(res); // true
+   *   console.log(order); // [[1, 'a']]
+   * });
+   *
+   */
+  function some(collection, iterator, callback) {
+    callback = callback || noop;
+    detect(collection, iterator, done);
+
+    function done(err, res) {
+      if (err) {
+        return callback(err);
+      }
+      callback(null, !!res);
+    }
+  }
+
+  /**
+   * @memberof async
+   * @namespace someSeries
+   * @param {Array|Object} collection
+   * @param {Function} iterator
+   * @param {Function} callback
+   * @example
+   *
+   * // array
+   * var order = [];
+   * var array = [1, 3, 2];
+   * var iterator = function(num, done) {
+   *   setTimeout(function() {
+   *     order.push(num);
+   *     done(null, num % 2);
+   *   }, num * 10);
+   * };
+   * async.someSeries(array, iterator, function(err, res) {
+   *   console.log(res); // true
+   *   console.log(order); // [1]
+   * });
+   *
+   * @example
+   *
+   * // array with index
+   * var order = [];
+   * var array = [1, 3, 2];
+   * var iterator = function(num, index, done) {
+   *   setTimeout(function() {
+   *     order.push([num, index]);
+   *     done(null, num % 2);
+   *   }, num * 10);
+   * };
+   * async.someSeries(array, iterator, function(err, res) {
+   *   console.log(res); // true
+   *   console.log(order); // [[1, 0]]
+   * });
+   *
+   * @example
+   *
+   * // object
+   * var order = [];
+   * var object = { a: 1, b: 3, c: 2 };
+   * var iterator = function(num, done) {
+   *   setTimeout(function() {
+   *     order.push(num);
+   *     done(null, num % 2);
+   *   }, num * 10);
+   * };
+   * async.someSeries(object, iterator, function(err, res) {
+   *   console.log(res); // true
+   *   console.log(order); // [1]
+   * });
+   *
+   * @example
+   *
+   * // object with key
+   * var order = [];
+   * var object = { a: 1, b: 3, c: 2 };
+   * var iterator = function(num, key, done) {
+   *   setTimeout(function() {
+   *     order.push([num, key]);
+   *     done(null, num % 2);
+   *   }, num * 10);
+   * };
+   * async.someSeries(object, iterator, function(err, res) {
+   *   console.log(res); // true
+   *   console.log(order); // [[1, 'a']]
+   * });
+   *
+   */
+  function someSeries(collection, iterator, callback) {
+    callback = callback || noop;
+    detectSeries(collection, iterator, done);
+
+    function done(err, res) {
+      if (err) {
+        return callback(err);
+      }
+      callback(null, !!res);
+    }
+  }
+
+  /**
+   * @memberof async
+   * @namespace someLimit
+   * @param {Array|Object} collection
+   * @param {number} limit - limit >= 1
+   * @param {Function} iterator
+   * @param {Function} callback
+   * @example
+   *
+   * // array
+   * var order = [];
+   * var array = [1, 5, 3, 4, 2];
+   * var iterator = function(num, done) {
+   *   setTimeout(function() {
+   *     order.push(num);
+   *     done(null, num % 2);
+   *   }, num * 10);
+   * };
+   * async.someLimit(array, 2, iterator, function(err, res) {
+   *   console.log(res); // true
+   *   console.log(order); // [1]
+   * });
+   *
+   * @example
+   *
+   * // array with index
+   * var order = [];
+   * var array = [1, 5, 3, 4, 2];
+   * var iterator = function(num, index, done) {
+   *   setTimeout(function() {
+   *     order.push([num, index]);
+   *     done(null, num % 2);
+   *   }, num * 10);
+   * };
+   * async.someLimit(array, 2, iterator, function(err, res) {
+   *   console.log(res); // true
+   *   console.log(order); // [[1, 0]]
+   * });
+   *
+   * @example
+   *
+   * // object
+   * var order = [];
+   * var object = { a: 1, b: 5, c: 3, d: 4, e: 2 };
+   * var iterator = function(num, done) {
+   *   setTimeout(function() {
+   *     order.push(num);
+   *     done(null, num % 2);
+   *   }, num * 10);
+   * };
+   * async.someLimit(object, 2, iterator, function(err, res) {
+   *   console.log(res); // true
+   *   console.log(order); // [1]
+   * });
+   *
+   * @example
+   *
+   * // object with key
+   * var order = [];
+   * var object = { a: 1, b: 5, c: 3, d: 4, e: 2 };
+   * var iterator = function(num, key, done) {
+   *   setTimeout(function() {
+   *     order.push([num, key]);
+   *     done(null, num % 2);
+   *   }, num * 10);
+   * };
+   * async.someLimit(object, 2, iterator, function(err, res) {
+   *   console.log(res); // true
+   *   console.log(order); // [[1, 'a']]
+   * });
+   *
+   */
+  function someLimit(collection, limit, iterator, callback) {
+    callback = callback || noop;
+    detectLimit(collection, limit, iterator, done);
+
+    function done(err, res) {
+      if (err) {
+        return callback(err);
+      }
+      callback(null, !!res);
+    }
+  }
+
+  /**
+   * @private
+   * @param {Function} arrayEach
+   * @param {Function} baseEach
+   * @param {Function} symbolEach
+   */
+  function createEvery(arrayEach, baseEach, symbolEach) {
+    var deny = createDetect(arrayEach, baseEach, symbolEach, false);
+
+    return function every(collection, iterator, callback) {
+      callback = callback || noop;
+      deny(collection, iterator, done);
+
+      function done(err, res) {
+        if (err) {
+          return callback(err);
+        }
+        callback(null, !res);
+      }
+    };
+  }
+
+  /**
+   * @private
+   */
+  function createEverySeries() {
+    var denySeries = createDetectSeries(false);
+
+    return function everySeries(collection, iterator, callback) {
+      callback = callback || noop;
+      denySeries(collection, iterator, done);
+
+      function done(err, res) {
+        if (err) {
+          return callback(err);
+        }
+        callback(null, !res);
+      }
+    };
+  }
+
+  /**
+   * @private
+   */
+  function createEveryLimit() {
+    var denyLimit = createDetectLimit(false);
+
+    return function everyLimit(collection, limit, iterator, callback) {
+      callback = callback || noop;
+      denyLimit(collection, limit, iterator, done);
+
+      function done(err, res) {
+        if (err) {
+          return callback(err);
+        }
+        callback(null, !res);
+      }
+    };
+  }
+
+  /**
+   * @private
+   * @param {Function} arrayEach
+   * @param {Function} baseEach
+   * @param {Function} symbolEach
+   */
+  function createConcat(arrayEach, baseEach, symbolEach) {
+    return function concat(collection, iterator, callback) {
+      callback = callback || noop;
+      var size, result;
+      var completed = 0;
+
+      if (isArray(collection)) {
+        size = collection.length;
+        result = Array(size);
+        arrayEach(collection, iterator, createCallback);
+      } else if (!collection) {
+      } else if (iteratorSymbol && collection[iteratorSymbol]) {
+        result = [];
+        size = symbolEach(collection, iterator, createCallback);
+        size && size === completed && callback(null, result);
+      } else if (typeof collection === obj) {
+        var keys = nativeKeys(collection);
+        size = keys.length;
+        result = Array(size);
+        baseEach(collection, iterator, createCallback, keys);
+      }
+      if (!size) {
+        callback(null, []);
+      }
+
+      function createCallback(index) {
+        return function done(err, res) {
+          if (index === null) {
+            throwError();
+          }
+          if (err) {
+            index = null;
+            callback = once(callback);
+            arrayEachSync(result, function(array, index) {
+              if (array === undefined) {
+                result[index] = noop;
+              }
+            });
+            callback(err, makeConcatResult(result));
+            return;
+          }
+          switch (arguments.length) {
+            case 0:
+            case 1:
+              result[index] = noop;
+              break;
+            case 2:
+              result[index] = res;
+              break;
+            default:
+              result[index] = slice(arguments, 1);
+              break;
+          }
+          index = null;
+          if (++completed === size) {
+            callback(null, makeConcatResult(result));
+          }
+        };
+      }
+    };
+  }
+
+  /**
+   * @memberof async
+   * @namespace concatSeries
+   * @param {Array|Object} collection
+   * @param {Function} iterator
+   * @param {Function} callback
+   * @example
+   *
+   * // array
+   * var order = [];
+   * var array = [1, 3, 2];
+   * var iterator = function(num, done) {
+   *   setTimeout(function() {
+   *     order.push(num);
+   *     done(null, [num]);
+   *   }, num * 10);
+   * };
+   * async.concatSeries(array, iterator, function(err, res) {
+   *   console.log(res); // [1, 3, 2];
+   *   console.log(order); // [1, 3, 2]
+   * });
+   *
+   * @example
+   *
+   * // array with index
+   * var order = [];
+   * var array = [1, 3, 2];
+   * var iterator = function(num, index, done) {
+   *   setTimeout(function() {
+   *     order.push([num, index]);
+   *     done(null, [num]);
+   *   }, num * 10);
+   * };
+   * async.concatSeries(array, iterator, function(err, res) {
+   *   console.log(res); // [1, 3, 2]
+   *   console.log(order); // [[1, 0], [3, 1], [2, 2]]
+   * });
+   *
+   * @example
+   *
+   * // object
+   * var order = [];
+   * var object = { a: 1, b: 3, c: 2 };
+   * var iterator = function(num, done) {
+   *   setTimeout(function() {
+   *     order.push(num);
+   *     done(null, [num]);
+   *   }, num * 10);
+   * };
+   * async.concatSeries(object, iterator, function(err, res) {
+   *   console.log(res); // [1, 3, 2]
+   *   console.log(order); // [1, 3, 2]
+   * });
+   *
+   * @example
+   *
+   * // object with key
+   * var order = [];
+   * var object = { a: 1, b: 3, c: 2 };
+   * var iterator = function(num, key, done) {
+   *   setTimeout(function() {
+   *     order.push([num, key]);
+   *     done(null, [num]);
+   *   }, num * 10);
+   * };
+   * async.concatSeries(object, iterator, function(err, res) {
+   *   console.log(res); // [1, 3, 2]
+   *   console.log(order); // [[1, 'a'], [3, 'b'], [2, 'c']]
+   * });
+   *
+   */
+  function concatSeries(collection, iterator, callback) {
+    callback = onlyOnce(callback || noop);
+    var size, key, keys, iter, item, iterate;
+    var sync = false;
+    var result = [];
+    var completed = 0;
+
+    if (isArray(collection)) {
+      size = collection.length;
+      iterate = iterator.length === 3 ? arrayIteratorWithIndex : arrayIterator;
+    } else if (!collection) {
+    } else if (iteratorSymbol && collection[iteratorSymbol]) {
+      size = Infinity;
+      iter = collection[iteratorSymbol]();
+      iterate = iterator.length === 3 ? symbolIteratorWithKey : symbolIterator;
+    } else if (typeof collection === obj) {
+      keys = nativeKeys(collection);
+      size = keys.length;
+      iterate = iterator.length === 3 ? objectIteratorWithKey : objectIterator;
+    }
+    if (!size) {
+      return callback(null, result);
+    }
+    iterate();
+
+    function arrayIterator() {
+      iterator(collection[completed], done);
+    }
+
+    function arrayIteratorWithIndex() {
+      iterator(collection[completed], completed, done);
+    }
+
+    function symbolIterator() {
+      item = iter.next();
+      item.done ? callback(null, result) : iterator(item.value, done);
+    }
+
+    function symbolIteratorWithKey() {
+      item = iter.next();
+      item.done ? callback(null, result) : iterator(item.value, completed, done);
+    }
+
+    function objectIterator() {
+      iterator(collection[keys[completed]], done);
+    }
+
+    function objectIteratorWithKey() {
+      key = keys[completed];
+      iterator(collection[key], key, done);
+    }
+
+    function done(err, array) {
+      if (isArray(array)) {
+        nativePush.apply(result, array);
+      } else if (arguments.length >= 2) {
+        nativePush.apply(result, slice(arguments, 1));
+      }
+      if (err) {
+        callback(err, result);
+      } else if (++completed === size) {
+        iterate = throwError;
+        callback(null, result);
+      } else if (sync) {
+        nextTick(iterate);
+      } else {
+        sync = true;
+        iterate();
+      }
+      sync = false;
+    }
+  }
+
+  /**
+   * @memberof async
+   * @namespace concatLimit
+   * @param {Array|Object} collection
+   * @param {number} limit - limit >= 1
+   * @param {Function} iterator
+   * @param {Function} callback
+   * @example
+   *
+   * // array
+   * var order = [];
+   * var array = [1, 5, 3, 4, 2];
+   * var iterator = function(num, done) {
+   *   setTimeout(function() {
+   *     order.push(num);
+   *     done(null, [num]);
+   *   }, num * 10);
+   * };
+   * async.concatLimit(array, 2, iterator, function(err, res) {
+   *   console.log(res); // [1, 3, 5, 2, 4]
+   *   console.log(order); // [1, 3, 5, 2, 4]
+   * });
+   *
+   * @example
+   *
+   * // array with index
+   * var order = [];
+   * var array = [1, 5, 3, 4, 2];
+   * var iterator = function(num, index, done) {
+   *   setTimeout(function() {
+   *     order.push([num, index]);
+   *     done(null, [num]);
+   *   }, num * 10);
+   * };
+   * async.cocnatLimit(array, 2, iterator, function(err, res) {
+   *   console.log(res); // [1, 3, 5, 2, 4]
+   *   console.log(order); // [[1, 0], [3, 2], [5, 1], [2, 4], [4, 3]]
+   * });
+   *
+   * @example
+   *
+   * // object
+   * var order = [];
+   * var object = { a: 1, b: 5, c: 3, d: 4, e: 2 };
+   * var iterator = function(num, done) {
+   *   setTimeout(function() {
+   *     order.push(num);
+   *     done(null, [num]);
+   *   }, num * 10);
+   * };
+   * async.concatLimit(object, 2, iterator, function(err, res) {
+   *   console.log(res); // [1, 3, 5, 2, 4]
+   *   console.log(order); // [1, 3, 5, 2, 4]
+   * });
+   *
+   * @example
+   *
+   * // object with key
+   * var order = [];
+   * var object = { a: 1, b: 5, c: 3, d: 4, e: 2 };
+   * var iterator = function(num, key, done) {
+   *   setTimeout(function() {
+   *     order.push([num, key]);
+   *     done(null, num);
+   *   }, num * 10);
+   * };
+   * async.cocnatLimit(object, 2, iterator, function(err, res) {
+   *   console.log(res); // [1, 3, 5, 2, 4]
+   *   console.log(order); // [[1, 'a'], [3, 'c'], [5, 'b'], [2, 'e'], [4, 'd']]
+   * });
+   *
+   */
+  function concatLimit(collection, limit, iterator, callback) {
+    callback = callback || noop;
+    var size, key, iter, item, iterate, result;
+    var sync = false;
+    var started = 0;
+    var completed = 0;
+
+    if (isArray(collection)) {
+      size = collection.length;
+      iterate = iterator.length === 3 ? arrayIteratorWithIndex : arrayIterator;
+    } else if (!collection) {
+    } else if (iteratorSymbol && collection[iteratorSymbol]) {
+      size = Infinity;
+      result = [];
+      iter = collection[iteratorSymbol]();
+      iterate = iterator.length === 3 ? symbolIteratorWithKey : symbolIterator;
+    } else if (typeof collection === obj) {
+      var keys = nativeKeys(collection);
+      size = keys.length;
+      iterate = iterator.length === 3 ? objectIteratorWithKey : objectIterator;
+    }
+    if (!size || isNaN(limit) || limit < 1) {
+      return callback(null, []);
+    }
+    result = result || Array(size);
+    timesSync(limit > size ? size : limit, iterate);
+
+    function arrayIterator() {
+      if (started < size) {
+        iterator(collection[started], createCallback(started++));
+      }
+    }
+
+    function arrayIteratorWithIndex() {
+      if (started < size) {
+        iterator(collection[started], started, createCallback(started++));
+      }
+    }
+
+    function symbolIterator() {
+      item = iter.next();
+      if (item.done === false) {
+        iterator(item.value, createCallback(started++));
+      } else if (completed === started && iterator !== noop) {
+        iterator = noop;
+        callback(null, makeConcatResult(result));
+      }
+    }
+
+    function symbolIteratorWithKey() {
+      item = iter.next();
+      if (item.done === false) {
+        iterator(item.value, started, createCallback(started++));
+      } else if (completed === started && iterator !== noop) {
+        iterator = noop;
+        callback(null, makeConcatResult(result));
+      }
+    }
+
+    function objectIterator() {
+      if (started < size) {
+        iterator(collection[keys[started]], createCallback(started++));
+      }
+    }
+
+    function objectIteratorWithKey() {
+      if (started < size) {
+        key = keys[started];
+        iterator(collection[key], key, createCallback(started++));
+      }
+    }
+
+    function createCallback(index) {
+      return function(err, res) {
+        if (index === null) {
+          throwError();
+        }
+        if (err) {
+          index = null;
+          iterate = noop;
+          callback = once(callback);
+          arrayEachSync(result, function(array, index) {
+            if (array === undefined) {
+              result[index] = noop;
+            }
+          });
+          callback(err, makeConcatResult(result));
+          return;
+        }
+        switch (arguments.length) {
+          case 0:
+          case 1:
+            result[index] = noop;
+            break;
+          case 2:
+            result[index] = res;
+            break;
+          default:
+            result[index] = slice(arguments, 1);
+            break;
+        }
+        index = null;
+        if (++completed === size) {
+          iterate = throwError;
+          callback(null, makeConcatResult(result));
+          callback = throwError;
+        } else if (sync) {
+          nextTick(iterate);
+        } else {
+          sync = true;
+          iterate();
+        }
+        sync = false;
+      };
+    }
+  }
+
+  /**
+   * @private
+   * @param {Function} arrayEach
+   * @param {Function} baseEach
+   * @param {Function} symbolEach
+   */
+  function createGroupBy(arrayEach, baseEach, symbolEach) {
+    return function groupBy(collection, iterator, callback) {
+      callback = callback || noop;
+      var size;
+      var completed = 0;
+      var result = {};
+
+      if (isArray(collection)) {
+        size = collection.length;
+        arrayEach(collection, iterator, createCallback);
+      } else if (!collection) {
+      } else if (iteratorSymbol && collection[iteratorSymbol]) {
+        size = symbolEach(collection, iterator, createCallback);
+        size && size === completed && callback(null, result);
+      } else if (typeof collection === obj) {
+        var keys = nativeKeys(collection);
+        size = keys.length;
+        baseEach(collection, iterator, createCallback, keys);
+      }
+      if (!size) {
+        callback(null, {});
+      }
+
+      function createCallback(value) {
+        var called = false;
+        return function done(err, key) {
+          if (called) {
+            throwError();
+          }
+          called = true;
+          if (err) {
+            callback = once(callback);
+            callback(err, objectClone(result));
+            return;
+          }
+          var array = result[key];
+          if (!array) {
+            result[key] = [value];
+          } else {
+            array.push(value);
+          }
+          if (++completed === size) {
+            callback(null, result);
+          }
+        };
+      }
+    };
+  }
+
+  /**
+   * @memberof async
+   * @namespace groupBySeries
+   * @param {Array|Object} collection
+   * @param {Function} iterator
+   * @param {Function} callback
+   * @example
+   *
+   * // array
+   * var order = [];
+   * var array = [4.2, 6.4, 6.1];
+   * var iterator = function(num, done) {
+   *   setTimeout(function() {
+   *     order.push(num);
+   *     done(null, Math.floor(num));
+   *   }, num * 10);
+   * };
+   * async.groupBySeries(array, iterator, function(err, res) {
+   *   console.log(res); // { '4': [4.2], '6': [6.4, 6.1] }
+   *   console.log(order); // [4.2, 6.4, 6.1]
+   * });
+   *
+   * @example
+   *
+   * // array with index
+   * var order = [];
+   * var array = [4.2, 6.4, 6.1];
+   * var iterator = function(num, index, done) {
+   *   setTimeout(function() {
+   *     order.push([num, index]);
+   *     done(null, Math.floor(num));
+   *   }, num * 10);
+   * };
+   * async.groupBySeries(array, iterator, function(err, res) {
+   *   console.log(res); // { '4': [4.2], '6': [6.4, 6.1] }
+   *   console.log(order); // [[4.2, 0], [6.4, 1], [6.1, 2]]
+   * });
+   *
+   * @example
+   *
+   * // object
+   * var order = [];
+   * var object = { a: 4.2, b: 6.4, c: 6.1 };
+   * var iterator = function(num, done) {
+   *   setTimeout(function() {
+   *     order.push(num);
+   *     done(null, Math.floor(num));
+   *   }, num * 10);
+   * };
+   * async.groupBySeries(object, iterator, function(err, res) {
+   *   console.log(res); // { '4': [4.2], '6': [6.4, 6.1] }
+   *   console.log(order); // [4.2, 6.4, 6.1]
+   * });
+   *
+   * @example
+   *
+   * // object with key
+   * var order = [];
+   * var object = { a: 4.2, b: 6.4, c: 6.1 };
+   * var iterator = function(num, key, done) {
+   *   setTimeout(function() {
+   *     order.push([num, key]);
+   *     done(null, Math.floor(num));
+   *   }, num * 10);
+   * };
+   * async.groupBySeries(object, iterator, function(err, res) {
+   *   console.log(res); // { '4': [4.2], '6': [6.4, 6.1] }
+   *   console.log(order); // [[4.2, 'a'], [6.4, 'b'], [6.1, 'c']]
+   * });
+   *
+   */
+  function groupBySeries(collection, iterator, callback) {
+    callback = onlyOnce(callback || noop);
+    var size, key, value, keys, iter, item, iterate;
+    var sync = false;
+    var completed = 0;
+    var result = {};
+
+    if (isArray(collection)) {
+      size = collection.length;
+      iterate = iterator.length === 3 ? arrayIteratorWithIndex : arrayIterator;
+    } else if (!collection) {
+    } else if (iteratorSymbol && collection[iteratorSymbol]) {
+      size = Infinity;
+      iter = collection[iteratorSymbol]();
+      iterate = iterator.length === 3 ? symbolIteratorWithKey : symbolIterator;
+    } else if (typeof collection === obj) {
+      keys = nativeKeys(collection);
+      size = keys.length;
+      iterate = iterator.length === 3 ? objectIteratorWithKey : objectIterator;
+    }
+    if (!size) {
+      return callback(null, result);
+    }
+    iterate();
+
+    function arrayIterator() {
+      value = collection[completed];
+      iterator(value, done);
+    }
+
+    function arrayIteratorWithIndex() {
+      value = collection[completed];
+      iterator(value, completed, done);
+    }
+
+    function symbolIterator() {
+      item = iter.next();
+      value = item.value;
+      item.done ? callback(null, result) : iterator(value, done);
+    }
+
+    function symbolIteratorWithKey() {
+      item = iter.next();
+      value = item.value;
+      item.done ? callback(null, result) : iterator(value, completed, done);
+    }
+
+    function objectIterator() {
+      value = collection[keys[completed]];
+      iterator(value, done);
+    }
+
+    function objectIteratorWithKey() {
+      key = keys[completed];
+      value = collection[key];
+      iterator(value, key, done);
+    }
+
+    function done(err, key) {
+      if (err) {
+        iterate = throwError;
+        callback = onlyOnce(callback);
+        callback(err, objectClone(result));
+        return;
+      }
+      var array = result[key];
+      if (!array) {
+        result[key] = [value];
+      } else {
+        array.push(value);
+      }
+      if (++completed === size) {
+        iterate = throwError;
+        callback(null, result);
+      } else if (sync) {
+        nextTick(iterate);
+      } else {
+        sync = true;
+        iterate();
+      }
+      sync = false;
+    }
+  }
+
+  /**
+   * @memberof async
+   * @namespace groupByLimit
+   * @param {Array|Object} collection
+   * @param {Function} iterator
+   * @param {Function} callback
+   * @example
+   *
+   * // array
+   * var order = [];
+   * var array = [1.1, 5.9, 3.2, 3.9, 2.1];
+   * var iterator = function(num, done) {
+   *   setTimeout(function() {
+   *     order.push(num);
+   *     done(null, Math.floor(num));
+   *   }, num * 10);
+   * };
+   * async.groupByLimit(array, 2, iterator, function(err, res) {
+   *   console.log(res); // { '1': [1.1], '3': [3.2, 3.9], '5': [5.9], '2': [2.1] }
+   *   console.log(order); // [1.1, 3.2, 5.9, 2.1, 3.9]
+   * });
+   *
+   * @example
+   *
+   * // array with index
+   * var order = [];
+   * var array = [1.1, 5.9, 3.2, 3.9, 2.1];
+   * var iterator = function(num, index, done) {
+   *   setTimeout(function() {
+   *     order.push([num, index]);
+   *     done(null, Math.floor(num));
+   *   }, num * 10);
+   * };
+   * async.groupByLimit(array, 2, iterator, function(err, res) {
+   *   console.log(res); // { '1': [1.1], '3': [3.2, 3.9], '5': [5.9], '2': [2.1] }
+   *   console.log(order); // [[1.1, 0], [3.2, 2], [5.9, 1], [2.1, 4], [3.9, 3]]
+   * });
+   *
+   * @example
+   *
+   * // object
+   * var order = [];
+   * var object = { a: 1.1, b: 5.9, c: 3.2, d: 3.9, e: 2.1 }
+   * var iterator = function(num, done) {
+   *   setTimeout(function() {
+   *     order.push(num);
+   *     done(null, Math.floor(num));
+   *   }, num * 10);
+   * };
+   * async.groupByLimit(object, 2, iterator, function(err, res) {
+   *   console.log(res); // { '1': [1.1], '3': [3.2, 3.9], '5': [5.9], '2': [2.1] }
+   *   console.log(order); // [1.1, 3.2, 5.9, 2.1, 3.9]
+   * });
+   *
+   * @example
+   *
+   * // object with key
+   * var order = [];
+   * var object = { a: 1.1, b: 5.9, c: 3.2, d: 3.9, e: 2.1 }
+   * var iterator = function(num, key, done) {
+   *   setTimeout(function() {
+   *     order.push([num, key]);
+   *     done(null, Math.floor(num));
+   *   }, num * 10);
+   * };
+   * async.groupByLimit(object, 2, iterator, function(err, res) {
+   *   console.log(res); // { '1': [1.1], '3': [3.2, 3.9], '5': [5.9], '2': [2.1] }
+   *   console.log(order); // [[1.1, 'a'], [3.2, 'c'], [5.9, 'b'], [2.1, 'e'], [3.9, 'd']]
+   * });
+   *
+   */
+  function groupByLimit(collection, limit, iterator, callback) {
+    callback = callback || noop;
+    var size, index, key, value, keys, iter, item, iterate;
+    var sync = false;
+    var started = 0;
+    var completed = 0;
+    var result = {};
+
+    if (isArray(collection)) {
+      size = collection.length;
+      iterate = iterator.length === 3 ? arrayIteratorWithIndex : arrayIterator;
+    } else if (!collection) {
+    } else if (iteratorSymbol && collection[iteratorSymbol]) {
+      size = Infinity;
+      iter = collection[iteratorSymbol]();
+      iterate = iterator.length === 3 ? symbolIteratorWithKey : symbolIterator;
+    } else if (typeof collection === obj) {
+      keys = nativeKeys(collection);
+      size = keys.length;
+      iterate = iterator.length === 3 ? objectIteratorWithKey : objectIterator;
+    }
+    if (!size || isNaN(limit) || limit < 1) {
+      return callback(null, result);
+    }
+    timesSync(limit > size ? size : limit, iterate);
+
+    function arrayIterator() {
+      if (started < size) {
+        value = collection[started++];
+        iterator(value, createCallback(value));
+      }
+    }
+
+    function arrayIteratorWithIndex() {
+      index = started++;
+      if (index < size) {
+        value = collection[index];
+        iterator(value, index, createCallback(value));
+      }
+    }
+
+    function symbolIterator() {
+      item = iter.next();
+      if (item.done === false) {
+        started++;
+        value = item.value;
+        iterator(value, createCallback(value));
+      } else if (completed === started && iterator !== noop) {
+        iterator = noop;
+        callback(null, result);
+      }
+    }
+
+    function symbolIteratorWithKey() {
+      item = iter.next();
+      if (item.done === false) {
+        value = item.value;
+        iterator(value, started++, createCallback(value));
+      } else if (completed === started && iterator !== noop) {
+        iterator = noop;
+        callback(null, result);
+      }
+    }
+
+    function objectIterator() {
+      if (started < size) {
+        value = collection[keys[started++]];
+        iterator(value, createCallback(value));
+      }
+    }
+
+    function objectIteratorWithKey() {
+      if (started < size) {
+        key = keys[started++];
+        value = collection[key];
+        iterator(value, key, createCallback(value));
+      }
+    }
+
+    function createCallback(value) {
+      var called = false;
+      return function(err, key) {
+        if (called) {
+          throwError();
+        }
+        called = true;
+        if (err) {
+          iterate = noop;
+          callback = once(callback);
+          callback(err, objectClone(result));
+          return;
+        }
+        var array = result[key];
+        if (!array) {
+          result[key] = [value];
+        } else {
+          array.push(value);
+        }
+        if (++completed === size) {
+          callback(null, result);
+        } else if (sync) {
+          nextTick(iterate);
+        } else {
+          sync = true;
+          iterate();
+        }
+        sync = false;
+      };
+    }
+  }
+
+  /**
+   * @private
+   * @param {Function} arrayEach
+   * @param {Function} baseEach
+   */
+  function createParallel(arrayEach, baseEach) {
+    return function parallel(tasks, callback) {
+      callback = callback || noop;
+      var size, keys, result;
+      var completed = 0;
+
+      if (isArray(tasks)) {
+        size = tasks.length;
+        result = Array(size);
+        arrayEach(tasks, createCallback);
+      } else if (tasks && typeof tasks === obj) {
+        keys = nativeKeys(tasks);
+        size = keys.length;
+        result = {};
+        baseEach(tasks, createCallback, keys);
+      }
+      if (!size) {
+        callback(null, result);
+      }
+
+      function createCallback(key) {
+        return function(err, res) {
+          if (key === null) {
+            throwError();
+          }
+          if (err) {
+            key = null;
+            callback = once(callback);
+            callback(err, result);
+            return;
+          }
+          result[key] = arguments.length <= 2 ? res : slice(arguments, 1);
+          key = null;
+          if (++completed === size) {
+            callback(null, result);
+          }
+        };
+      }
+    };
+  }
+
+  /**
+   * @memberof async
+   * @namespace series
+   * @param {Array|Object} tasks - functions
+   * @param {Function} callback
+   * @example
+   *
+   * var order = [];
+   * var tasks = [
+   *  function(done) {
+   *    setTimeout(function() {
+   *      order.push(1);
+   *      done(null, 1);
+   *    }, 10);
+   *  },
+   *  function(done) {
+   *    setTimeout(function() {
+   *      order.push(2);
+   *      done(null, 2);
+   *    }, 30);
+   *  },
+   *  function(done) {
+   *    setTimeout(function() {
+   *      order.push(3);
+   *      done(null, 3);
+   *    }, 40);
+   *  },
+   *  function(done) {
+   *    setTimeout(function() {
+   *      order.push(4);
+   *      done(null, 4);
+   *    }, 20);
+   *  }
+   * ];
+   * async.series(tasks, function(err, res) {
+   *   console.log(res); // [1, 2, 3, 4];
+   *   console.log(order); // [1, 2, 3, 4]
+   * });
+   *
+   * @example
+   *
+   * var order = [];
+   * var tasks = {
+   *   'a': function(done) {
+   *     setTimeout(function() {
+   *       order.push(1);
+   *       done(null, 1);
+   *     }, 10);
+   *   },
+   *   'b': function(done) {
+   *     setTimeout(function() {
+   *       order.push(2);
+   *       done(null, 2);
+   *     }, 30);
+   *   },
+   *   'c': function(done) {
+   *     setTimeout(function() {
+   *       order.push(3);
+   *       done(null, 3);
+   *     }, 40);
+   *   },
+   *   'd': function(done) {
+   *     setTimeout(function() {
+   *       order.push(4);
+   *       done(null, 4);
+   *     }, 20);
+   *   }
+   * };
+   * async.series(tasks, function(err, res) {
+   *   console.log(res); // { a: 1, b: 2, c: 3, d:4 }
+   *   console.log(order); // [1, 4, 2, 3]
+   * });
+   *
+   */
+  function series(tasks, callback) {
+    callback = callback || noop;
+    var size, key, keys, result, iterate;
+    var sync = false;
+    var completed = 0;
+
+    if (isArray(tasks)) {
+      size = tasks.length;
+      result = Array(size);
+      iterate = arrayIterator;
+    } else if (tasks && typeof tasks === obj) {
+      keys = nativeKeys(tasks);
+      size = keys.length;
+      result = {};
+      iterate = objectIterator;
+    } else {
+      return callback(null);
+    }
+    if (!size) {
+      return callback(null, result);
+    }
+    iterate();
+
+    function arrayIterator() {
+      key = completed;
+      tasks[completed](done);
+    }
+
+    function objectIterator() {
+      key = keys[completed];
+      tasks[key](done);
+    }
+
+    function done(err, res) {
+      if (err) {
+        iterate = throwError;
+        callback = onlyOnce(callback);
+        callback(err, result);
+        return;
+      }
+      result[key] = arguments.length <= 2 ? res : slice(arguments, 1);
+      if (++completed === size) {
+        iterate = throwError;
+        callback(null, result);
+      } else if (sync) {
+        nextTick(iterate);
+      } else {
+        sync = true;
+        iterate();
+      }
+      sync = false;
+    }
+  }
+
+  /**
+   * @memberof async
+   * @namespace parallelLimit
+   * @param {Array|Object} tasks - functions
+   * @param {number} limit - limit >= 1
+   * @param {Function} callback
+   * @example
+   *
+   * var order = [];
+   * var tasks = [
+   *  function(done) {
+   *    setTimeout(function() {
+   *      order.push(1);
+   *      done(null, 1);
+   *    }, 10);
+   *  },
+   *  function(done) {
+   *    setTimeout(function() {
+   *      order.push(2);
+   *      done(null, 2);
+   *    }, 50);
+   *  },
+   *  function(done) {
+   *    setTimeout(function() {
+   *      order.push(3);
+   *      done(null, 3);
+   *    }, 30);
+   *  },
+   *  function(done) {
+   *    setTimeout(function() {
+   *      order.push(4);
+   *      done(null, 4);
+   *    }, 40);
+   *  }
+   * ];
+   * async.parallelLimit(tasks, 2, function(err, res) {
+   *   console.log(res); // [1, 2, 3, 4];
+   *   console.log(order); // [1, 3, 2, 4]
+   * });
+   *
+   * @example
+   *
+   * var order = [];
+   * var tasks = {
+   *   'a': function(done) {
+   *     setTimeout(function() {
+   *       order.push(1);
+   *       done(null, 1);
+   *     }, 10);
+   *   },
+   *   'b': function(done) {
+   *     setTimeout(function() {
+   *       order.push(2);
+   *       done(null, 2);
+   *     }, 50);
+   *   },
+   *   'c': function(done) {
+   *     setTimeout(function() {
+   *       order.push(3);
+   *       done(null, 3);
+   *     }, 20);
+   *   },
+   *   'd': function(done) {
+   *     setTimeout(function() {
+   *       order.push(4);
+   *       done(null, 4);
+   *     }, 40);
+   *   }
+   * };
+   * async.parallelLimit(tasks, 2, function(err, res) {
+   *   console.log(res); // { a: 1, b: 2, c: 3, d:4 }
+   *   console.log(order); // [1, 3, 2, 4]
+   * });
+   *
+   */
+  function parallelLimit(tasks, limit, callback) {
+    callback = callback || noop;
+    var size, index, key, keys, result, iterate;
+    var sync = false;
+    var started = 0;
+    var completed = 0;
+
+    if (isArray(tasks)) {
+      size = tasks.length;
+      result = Array(size);
+      iterate = arrayIterator;
+    } else if (tasks && typeof tasks === obj) {
+      keys = nativeKeys(tasks);
+      size = keys.length;
+      result = {};
+      iterate = objectIterator;
+    }
+    if (!size || isNaN(limit) || limit < 1) {
+      return callback(null, result);
+    }
+    timesSync(limit > size ? size : limit, iterate);
+
+    function arrayIterator() {
+      index = started++;
+      if (index < size) {
+        tasks[index](createCallback(index));
+      }
+    }
+
+    function objectIterator() {
+      if (started < size) {
+        key = keys[started++];
+        tasks[key](createCallback(key));
+      }
+    }
+
+    function createCallback(key) {
+      return function(err, res) {
+        if (key === null) {
+          throwError();
+        }
+        if (err) {
+          key = null;
+          iterate = noop;
+          callback = once(callback);
+          callback(err, result);
+          return;
+        }
+        result[key] = arguments.length <= 2 ? res : slice(arguments, 1);
+        key = null;
+        if (++completed === size) {
+          callback(null, result);
+        } else if (sync) {
+          nextTick(iterate);
+        } else {
+          sync = true;
+          iterate();
+        }
+        sync = false;
+      };
+    }
+  }
+
+  /**
+   * @memberof async
+   * @namespace tryEach
+   * @param {Array|Object} tasks - functions
+   * @param {Function} callback
+   * @example
+   *
+   * var tasks = [
+   *  function(done) {
+   *    setTimeout(function() {
+   *      done(new Error('error'));
+   *    }, 10);
+   *  },
+   *  function(done) {
+   *    setTimeout(function() {
+   *      done(null, 2);
+   *    }, 10);
+   *  }
+   * ];
+   * async.tryEach(tasks, function(err, res) {
+   *   console.log(res); // 2
+   * });
+   *
+   * @example
+   *
+   * var tasks = [
+   *  function(done) {
+   *    setTimeout(function() {
+   *      done(new Error('error1'));
+   *    }, 10);
+   *  },
+   *  function(done) {
+   *    setTimeout(function() {
+   *      done(new Error('error2');
+   *    }, 10);
+   *  }
+   * ];
+   * async.tryEach(tasks, function(err, res) {
+   *   console.log(err); // error2
+   *   console.log(res); // undefined
+   * });
+   *
+   */
+  function tryEach(tasks, callback) {
+    callback = callback || noop;
+    var size, keys, iterate;
+    var sync = false;
+    var completed = 0;
+
+    if (isArray(tasks)) {
+      size = tasks.length;
+      iterate = arrayIterator;
+    } else if (tasks && typeof tasks === obj) {
+      keys = nativeKeys(tasks);
+      size = keys.length;
+      iterate = objectIterator;
+    }
+    if (!size) {
+      return callback(null);
+    }
+    iterate();
+
+    function arrayIterator() {
+      tasks[completed](done);
+    }
+
+    function objectIterator() {
+      tasks[keys[completed]](done);
+    }
+
+    function done(err, res) {
+      if (!err) {
+        if (arguments.length <= 2) {
+          callback(null, res);
+        } else {
+          callback(null, slice(arguments, 1));
+        }
+      } else if (++completed === size) {
+        callback(err);
+      } else {
+        sync = true;
+        iterate();
+      }
+      sync = false;
+    }
+  }
+
+  /**
+   * check for waterfall tasks
+   * @private
+   * @param {Array} tasks
+   * @param {Function} callback
+   * @return {boolean}
+   */
+  function checkWaterfallTasks(tasks, callback) {
+    if (!isArray(tasks)) {
+      callback(new Error('First argument to waterfall must be an array of functions'));
+      return false;
+    }
+    if (tasks.length === 0) {
+      callback(null);
+      return false;
+    }
+    return true;
+  }
+
+  /**
+   * check for waterfall tasks
+   * @private
+   * @param {function} func
+   * @param {Array|Object} args - arguments
+   * @return {function} next
+   */
+  function waterfallIterator(func, args, next) {
+    switch (args.length) {
+      case 0:
+      case 1:
+        return func(next);
+      case 2:
+        return func(args[1], next);
+      case 3:
+        return func(args[1], args[2], next);
+      case 4:
+        return func(args[1], args[2], args[3], next);
+      case 5:
+        return func(args[1], args[2], args[3], args[4], next);
+      case 6:
+        return func(args[1], args[2], args[3], args[4], args[5], next);
+      default:
+        args = slice(args, 1);
+        args.push(next);
+        return func.apply(null, args);
+    }
+  }
+
+  /**
+   * @memberof async
+   * @namespace waterfall
+   * @param {Array} tasks - functions
+   * @param {Function} callback
+   * @example
+   *
+   * var order = [];
+   * var tasks = [
+   *   function(next) {
+   *     setTimeout(function() {
+   *       order.push(1);
+   *       next(null, 1);
+   *     }, 10);
+   *   },
+   *   function(arg1, next) {
+   *     setTimeout(function() {
+   *       order.push(2);
+   *       next(null, 1, 2);
+   *     }, 30);
+   *   },
+   *   function(arg1, arg2, next) {
+   *     setTimeout(function() {
+   *       order.push(3);
+   *       next(null, 3);
+   *     }, 20);
+   *   },
+   *   function(arg1, next) {
+   *     setTimeout(function() {
+   *       order.push(4);
+   *       next(null, 1, 2, 3, 4);
+   *     }, 40);
+   *   }
+   * ];
+   * async.waterfall(tasks, function(err, arg1, arg2, arg3, arg4) {
+   *   console.log(arg1, arg2, arg3, arg4); // 1 2 3 4
+   * });
+   *
+   */
+  function waterfall(tasks, callback) {
+    callback = callback || noop;
+    if (!checkWaterfallTasks(tasks, callback)) {
+      return;
+    }
+    var func, args, done, sync;
+    var completed = 0;
+    var size = tasks.length;
+    waterfallIterator(tasks[0], [], createCallback(0));
+
+    function iterate() {
+      waterfallIterator(func, args, createCallback(func));
+    }
+
+    function createCallback(index) {
+      return function next(err, res) {
+        if (index === undefined) {
+          callback = noop;
+          throwError();
+        }
+        index = undefined;
+        if (err) {
+          done = callback;
+          callback = throwError;
+          done(err);
+          return;
+        }
+        if (++completed === size) {
+          done = callback;
+          callback = throwError;
+          if (arguments.length <= 2) {
+            done(err, res);
+          } else {
+            done.apply(null, createArray(arguments));
+          }
+          return;
+        }
+        if (sync) {
+          args = arguments;
+          func = tasks[completed] || throwError;
+          nextTick(iterate);
+        } else {
+          sync = true;
+          waterfallIterator(tasks[completed] || throwError, arguments, createCallback(completed));
+        }
+        sync = false;
+      };
+    }
+  }
+
+  /**
+   * `angelFall` is like `waterfall` and inject callback to last argument of next task.
+   *
+   * @memberof async
+   * @namespace angelFall
+   * @param {Array} tasks - functions
+   * @param {Function} callback
+   * @example
+   *
+   * var order = [];
+   * var tasks = [
+   *   function(next) {
+   *     setTimeout(function() {
+   *       order.push(1);
+   *       next(null, 1);
+   *     }, 10);
+   *   },
+   *   function(arg1, empty, next) {
+   *     setTimeout(function() {
+   *       order.push(2);
+   *       next(null, 1, 2);
+   *     }, 30);
+   *   },
+   *   function(next) {
+   *     setTimeout(function() {
+   *       order.push(3);
+   *       next(null, 3);
+   *     }, 20);
+   *   },
+   *   function(arg1, empty1, empty2, empty3, next) {
+   *     setTimeout(function() {
+   *       order.push(4);
+   *       next(null, 1, 2, 3, 4);
+   *     }, 40);
+   *   }
+   * ];
+   * async.angelFall(tasks, function(err, arg1, arg2, arg3, arg4) {
+   *   console.log(arg1, arg2, arg3, arg4); // 1 2 3 4
+   * });
+   *
+   */
+  function angelFall(tasks, callback) {
+    callback = callback || noop;
+    if (!checkWaterfallTasks(tasks, callback)) {
+      return;
+    }
+    var completed = 0;
+    var sync = false;
+    var size = tasks.length;
+    var func = tasks[completed];
+    var args = [];
+    var iterate = function() {
+      switch (func.length) {
+        case 0:
+          try {
+            next(null, func());
+          } catch (e) {
+            next(e);
+          }
+          return;
+        case 1:
+          return func(next);
+        case 2:
+          return func(args[1], next);
+        case 3:
+          return func(args[1], args[2], next);
+        case 4:
+          return func(args[1], args[2], args[3], next);
+        case 5:
+          return func(args[1], args[2], args[3], args[4], next);
+        default:
+          args = slice(args, 1);
+          args[func.length - 1] = next;
+          return func.apply(null, args);
+      }
+    };
+    iterate();
+
+    function next(err, res) {
+      if (err) {
+        iterate = throwError;
+        callback = onlyOnce(callback);
+        callback(err);
+        return;
+      }
+      if (++completed === size) {
+        iterate = throwError;
+        var done = callback;
+        callback = throwError;
+        if (arguments.length === 2) {
+          done(err, res);
+        } else {
+          done.apply(null, createArray(arguments));
+        }
+        return;
+      }
+      func = tasks[completed];
+      args = arguments;
+      if (sync) {
+        nextTick(iterate);
+      } else {
+        sync = true;
+        iterate();
+      }
+      sync = false;
+    }
+  }
+
+  /**
+   * @memberof async
+   * @namespace whilst
+   * @param {Function} test
+   * @param {Function} iterator
+   * @param {Function} callback
+   */
+  function whilst(test, iterator, callback) {
+    callback = callback || noop;
+    var sync = false;
+    if (test()) {
+      iterate();
+    } else {
+      callback(null);
+    }
+
+    function iterate() {
+      if (sync) {
+        nextTick(next);
+      } else {
+        sync = true;
+        iterator(done);
+      }
+      sync = false;
+    }
+
+    function next() {
+      iterator(done);
+    }
+
+    function done(err, arg) {
+      if (err) {
+        return callback(err);
+      }
+      if (arguments.length <= 2) {
+        if (test(arg)) {
+          iterate();
+        } else {
+          callback(null, arg);
+        }
+        return;
+      }
+      arg = slice(arguments, 1);
+      if (test.apply(null, arg)) {
+        iterate();
+      } else {
+        callback.apply(null, [null].concat(arg));
+      }
+    }
+  }
+
+  /**
+   * @memberof async
+   * @namespace doWhilst
+   * @param {Function} iterator
+   * @param {Function} test
+   * @param {Function} callback
+   */
+  function doWhilst(iterator, test, callback) {
+    callback = callback || noop;
+    var sync = false;
+    next();
+
+    function iterate() {
+      if (sync) {
+        nextTick(next);
+      } else {
+        sync = true;
+        iterator(done);
+      }
+      sync = false;
+    }
+
+    function next() {
+      iterator(done);
+    }
+
+    function done(err, arg) {
+      if (err) {
+        return callback(err);
+      }
+      if (arguments.length <= 2) {
+        if (test(arg)) {
+          iterate();
+        } else {
+          callback(null, arg);
+        }
+        return;
+      }
+      arg = slice(arguments, 1);
+      if (test.apply(null, arg)) {
+        iterate();
+      } else {
+        callback.apply(null, [null].concat(arg));
+      }
+    }
+  }
+
+  /**
+   * @memberof async
+   * @namespace until
+   * @param {Function} test
+   * @param {Function} iterator
+   * @param {Function} callback
+   */
+  function until(test, iterator, callback) {
+    callback = callback || noop;
+    var sync = false;
+    if (!test()) {
+      iterate();
+    } else {
+      callback(null);
+    }
+
+    function iterate() {
+      if (sync) {
+        nextTick(next);
+      } else {
+        sync = true;
+        iterator(done);
+      }
+      sync = false;
+    }
+
+    function next() {
+      iterator(done);
+    }
+
+    function done(err, arg) {
+      if (err) {
+        return callback(err);
+      }
+      if (arguments.length <= 2) {
+        if (!test(arg)) {
+          iterate();
+        } else {
+          callback(null, arg);
+        }
+        return;
+      }
+      arg = slice(arguments, 1);
+      if (!test.apply(null, arg)) {
+        iterate();
+      } else {
+        callback.apply(null, [null].concat(arg));
+      }
+    }
+  }
+
+  /**
+   * @memberof async
+   * @namespace doUntil
+   * @param {Function} iterator
+   * @param {Function} test
+   * @param {Function} callback
+   */
+  function doUntil(iterator, test, callback) {
+    callback = callback || noop;
+    var sync = false;
+    next();
+
+    function iterate() {
+      if (sync) {
+        nextTick(next);
+      } else {
+        sync = true;
+        iterator(done);
+      }
+      sync = false;
+    }
+
+    function next() {
+      iterator(done);
+    }
+
+    function done(err, arg) {
+      if (err) {
+        return callback(err);
+      }
+      if (arguments.length <= 2) {
+        if (!test(arg)) {
+          iterate();
+        } else {
+          callback(null, arg);
+        }
+        return;
+      }
+      arg = slice(arguments, 1);
+      if (!test.apply(null, arg)) {
+        iterate();
+      } else {
+        callback.apply(null, [null].concat(arg));
+      }
+    }
+  }
+
+  /**
+   * @memberof async
+   * @namespace during
+   * @param {Function} test
+   * @param {Function} iterator
+   * @param {Function} callback
+   */
+  function during(test, iterator, callback) {
+    callback = callback || noop;
+    _test();
+
+    function _test() {
+      test(iterate);
+    }
+
+    function iterate(err, truth) {
+      if (err) {
+        return callback(err);
+      }
+      if (truth) {
+        iterator(done);
+      } else {
+        callback(null);
+      }
+    }
+
+    function done(err) {
+      if (err) {
+        return callback(err);
+      }
+      _test();
+    }
+  }
+
+  /**
+   * @memberof async
+   * @namespace doDuring
+   * @param {Function} test
+   * @param {Function} iterator
+   * @param {Function} callback
+   */
+  function doDuring(iterator, test, callback) {
+    callback = callback || noop;
+    iterate(null, true);
+
+    function iterate(err, truth) {
+      if (err) {
+        return callback(err);
+      }
+      if (truth) {
+        iterator(done);
+      } else {
+        callback(null);
+      }
+    }
+
+    function done(err, res) {
+      if (err) {
+        return callback(err);
+      }
+      switch (arguments.length) {
+        case 0:
+        case 1:
+          test(iterate);
+          break;
+        case 2:
+          test(res, iterate);
+          break;
+        default:
+          var args = slice(arguments, 1);
+          args.push(iterate);
+          test.apply(null, args);
+          break;
+      }
+    }
+  }
+
+  /**
+   * @memberof async
+   * @namespace forever
+   */
+  function forever(iterator, callback) {
+    var sync = false;
+    iterate();
+
+    function iterate() {
+      iterator(next);
+    }
+
+    function next(err) {
+      if (err) {
+        if (callback) {
+          return callback(err);
+        }
+        throw err;
+      }
+      if (sync) {
+        nextTick(iterate);
+      } else {
+        sync = true;
+        iterate();
+      }
+      sync = false;
+    }
+  }
+
+  /**
+   * @memberof async
+   * @namespace compose
+   */
+  function compose() {
+    return seq.apply(null, reverse(arguments));
+  }
+
+  /**
+   * @memberof async
+   * @namespace seq
+   */
+  function seq(/* functions... */) {
+    var fns = createArray(arguments);
+
+    return function() {
+      var self = this;
+      var args = createArray(arguments);
+      var callback = args[args.length - 1];
+      if (typeof callback === func) {
+        args.pop();
+      } else {
+        callback = noop;
+      }
+      reduce(fns, args, iterator, done);
+
+      function iterator(newargs, fn, callback) {
+        var func = function(err) {
+          var nextargs = slice(arguments, 1);
+          callback(err, nextargs);
+        };
+        newargs.push(func);
+        fn.apply(self, newargs);
+      }
+
+      function done(err, res) {
+        res = isArray(res) ? res : [res];
+        res.unshift(err);
+        callback.apply(self, res);
+      }
+    };
+  }
+
+  function createApplyEach(func) {
+    return function applyEach(fns /* arguments */) {
+      var go = function() {
+        var self = this;
+        var args = createArray(arguments);
+        var callback = args.pop() || noop;
+        return func(fns, iterator, callback);
+
+        function iterator(fn, done) {
+          fn.apply(self, args.concat([done]));
+        }
+      };
+      if (arguments.length > 1) {
+        var args = slice(arguments, 1);
+        return go.apply(this, args);
+      } else {
+        return go;
+      }
+    };
+  }
+
+  /**
+   * @see https://github.com/caolan/async/blob/master/lib/internal/DoublyLinkedList.js
+   */
+  function DLL() {
+    this.head = null;
+    this.tail = null;
+    this.length = 0;
+  }
+
+  DLL.prototype._removeLink = function(node) {
+    var prev = node.prev;
+    var next = node.next;
+    if (prev) {
+      prev.next = next;
+    } else {
+      this.head = next;
+    }
+    if (next) {
+      next.prev = prev;
+    } else {
+      this.tail = prev;
+    }
+    node.prev = null;
+    node.next = null;
+    this.length--;
+    return node;
+  };
+
+  DLL.prototype.empty = DLL;
+
+  DLL.prototype._setInitial = function(node) {
+    this.length = 1;
+    this.head = this.tail = node;
+  };
+
+  DLL.prototype.insertBefore = function(node, newNode) {
+    newNode.prev = node.prev;
+    newNode.next = node;
+    if (node.prev) {
+      node.prev.next = newNode;
+    } else {
+      this.head = newNode;
+    }
+    node.prev = newNode;
+    this.length++;
+  };
+
+  DLL.prototype.unshift = function(node) {
+    if (this.head) {
+      this.insertBefore(this.head, node);
+    } else {
+      this._setInitial(node);
+    }
+  };
+
+  DLL.prototype.push = function(node) {
+    var tail = this.tail;
+    if (tail) {
+      node.prev = tail;
+      node.next = tail.next;
+      this.tail = node;
+      tail.next = node;
+      this.length++;
+    } else {
+      this._setInitial(node);
+    }
+  };
+
+  DLL.prototype.shift = function() {
+    return this.head && this._removeLink(this.head);
+  };
+
+  DLL.prototype.splice = function(end) {
+    var task;
+    var tasks = [];
+    while (end-- && (task = this.shift())) {
+      tasks.push(task);
+    }
+    return tasks;
+  };
+
+  DLL.prototype.remove = function(test) {
+    var node = this.head;
+    while (node) {
+      if (test(node)) {
+        this._removeLink(node);
+      }
+      node = node.next;
+    }
+    return this;
+  };
+
+  /**
+   * @private
+   */
+  function baseQueue(isQueue, worker, concurrency, payload) {
+    if (concurrency === undefined) {
+      concurrency = 1;
+    } else if (isNaN(concurrency) || concurrency < 1) {
+      throw new Error('Concurrency must not be zero');
+    }
+
+    var workers = 0;
+    var workersList = [];
+    var _callback, _unshift;
+
+    var q = {
+      _tasks: new DLL(),
+      concurrency: concurrency,
+      payload: payload,
+      saturated: noop,
+      unsaturated: noop,
+      buffer: concurrency / 4,
+      empty: noop,
+      drain: noop,
+      error: noop,
+      started: false,
+      paused: false,
+      push: push,
+      kill: kill,
+      unshift: unshift,
+      remove: remove,
+      process: isQueue ? runQueue : runCargo,
+      length: getLength,
+      running: running,
+      workersList: getWorkersList,
+      idle: idle,
+      pause: pause,
+      resume: resume,
+      _worker: worker
+    };
+    return q;
+
+    function push(tasks, callback) {
+      _insert(tasks, callback);
+    }
+
+    function unshift(tasks, callback) {
+      _insert(tasks, callback, true);
+    }
+
+    function _exec(task) {
+      var item = {
+        data: task,
+        callback: _callback
+      };
+      if (_unshift) {
+        q._tasks.unshift(item);
+      } else {
+        q._tasks.push(item);
+      }
+      nextTick(q.process);
+    }
+
+    function _insert(tasks, callback, unshift) {
+      if (callback == null) {
+        callback = noop;
+      } else if (typeof callback !== 'function') {
+        throw new Error('task callback must be a function');
+      }
+      q.started = true;
+      var _tasks = isArray(tasks) ? tasks : [tasks];
+
+      if (tasks === undefined || !_tasks.length) {
+        if (q.idle()) {
+          nextTick(q.drain);
+        }
+        return;
+      }
+
+      _unshift = unshift;
+      _callback = callback;
+      arrayEachSync(_tasks, _exec);
+      // Avoid leaking the callback
+      _callback = undefined;
+    }
+
+    function kill() {
+      q.drain = noop;
+      q._tasks.empty();
+    }
+
+    function _next(q, tasks) {
+      var called = false;
+      return function done(err, res) {
+        if (called) {
+          throwError();
+        }
+        called = true;
+
+        workers--;
+        var task;
+        var index = -1;
+        var size = workersList.length;
+        var taskIndex = -1;
+        var taskSize = tasks.length;
+        var useApply = arguments.length > 2;
+        var args = useApply && createArray(arguments);
+        while (++taskIndex < taskSize) {
+          task = tasks[taskIndex];
+          while (++index < size) {
+            if (workersList[index] === task) {
+              if (index === 0) {
+                workersList.shift();
+              } else {
+                workersList.splice(index, 1);
+              }
+              index = size;
+              size--;
+            }
+          }
+          index = -1;
+          if (useApply) {
+            task.callback.apply(task, args);
+          } else {
+            task.callback(err, res);
+          }
+          if (err) {
+            q.error(err, task.data);
+          }
+        }
+
+        if (workers <= q.concurrency - q.buffer) {
+          q.unsaturated();
+        }
+
+        if (q._tasks.length + workers === 0) {
+          q.drain();
+        }
+        q.process();
+      };
+    }
+
+    function runQueue() {
+      while (!q.paused && workers < q.concurrency && q._tasks.length) {
+        var task = q._tasks.shift();
+        workers++;
+        workersList.push(task);
+        if (q._tasks.length === 0) {
+          q.empty();
+        }
+        if (workers === q.concurrency) {
+          q.saturated();
+        }
+        var done = _next(q, [task]);
+        worker(task.data, done);
+      }
+    }
+
+    function runCargo() {
+      while (!q.paused && workers < q.concurrency && q._tasks.length) {
+        var tasks = q._tasks.splice(q.payload || q._tasks.length);
+        var index = -1;
+        var size = tasks.length;
+        var data = Array(size);
+        while (++index < size) {
+          data[index] = tasks[index].data;
+        }
+        workers++;
+        nativePush.apply(workersList, tasks);
+        if (q._tasks.length === 0) {
+          q.empty();
+        }
+        if (workers === q.concurrency) {
+          q.saturated();
+        }
+        var done = _next(q, tasks);
+        worker(data, done);
+      }
+    }
+
+    function getLength() {
+      return q._tasks.length;
+    }
+
+    function running() {
+      return workers;
+    }
+
+    function getWorkersList() {
+      return workersList;
+    }
+
+    function idle() {
+      return q.length() + workers === 0;
+    }
+
+    function pause() {
+      q.paused = true;
+    }
+
+    function _resume() {
+      nextTick(q.process);
+    }
+
+    function resume() {
+      if (q.paused === false) {
+        return;
+      }
+      q.paused = false;
+      var count = q.concurrency < q._tasks.length ? q.concurrency : q._tasks.length;
+      timesSync(count, _resume);
+    }
+
+    /**
+     * @param {Function} test
+     */
+    function remove(test) {
+      q._tasks.remove(test);
+    }
+  }
+
+  /**
+   * @memberof async
+   * @namespace queue
+   */
+  function queue(worker, concurrency) {
+    return baseQueue(true, worker, concurrency);
+  }
+
+  /**
+   * @memberof async
+   * @namespace priorityQueue
+   */
+  function priorityQueue(worker, concurrency) {
+    var q = baseQueue(true, worker, concurrency);
+    q.push = push;
+    delete q.unshift;
+    return q;
+
+    function push(tasks, priority, callback) {
+      q.started = true;
+      priority = priority || 0;
+      var _tasks = isArray(tasks) ? tasks : [tasks];
+      var taskSize = _tasks.length;
+
+      if (tasks === undefined || taskSize === 0) {
+        if (q.idle()) {
+          nextTick(q.drain);
+        }
+        return;
+      }
+
+      callback = typeof callback === func ? callback : noop;
+      var nextNode = q._tasks.head;
+      while (nextNode && priority >= nextNode.priority) {
+        nextNode = nextNode.next;
+      }
+      while (taskSize--) {
+        var item = {
+          data: _tasks[taskSize],
+          priority: priority,
+          callback: callback
+        };
+        if (nextNode) {
+          q._tasks.insertBefore(nextNode, item);
+        } else {
+          q._tasks.push(item);
+        }
+        nextTick(q.process);
+      }
+    }
+  }
+
+  /**
+   * @memberof async
+   * @namespace cargo
+   */
+  function cargo(worker, payload) {
+    return baseQueue(false, worker, 1, payload);
+  }
+
+  /**
+   * @memberof async
+   * @namespace auto
+   * @param {Object} tasks
+   * @param {number} [concurrency]
+   * @param {Function} [callback]
+   */
+  function auto(tasks, concurrency, callback) {
+    if (typeof concurrency === func) {
+      callback = concurrency;
+      concurrency = null;
+    }
+    var keys = nativeKeys(tasks);
+    var rest = keys.length;
+    var results = {};
+    if (rest === 0) {
+      return callback(null, results);
+    }
+    var runningTasks = 0;
+    var readyTasks = new DLL();
+    var listeners = Object.create(null);
+    callback = onlyOnce(callback || noop);
+    concurrency = concurrency || rest;
+
+    baseEachSync(tasks, iterator, keys);
+    proceedQueue();
+
+    function iterator(task, key) {
+      // no dependencies
+      var _task, _taskSize;
+      if (!isArray(task)) {
+        _task = task;
+        _taskSize = 0;
+        readyTasks.push([_task, _taskSize, done]);
+        return;
+      }
+      var dependencySize = task.length - 1;
+      _task = task[dependencySize];
+      _taskSize = dependencySize;
+      if (dependencySize === 0) {
+        readyTasks.push([_task, _taskSize, done]);
+        return;
+      }
+      // dependencies
+      var index = -1;
+      while (++index < dependencySize) {
+        var dependencyName = task[index];
+        if (notInclude(keys, dependencyName)) {
+          var msg =
+            'async.auto task `' +
+            key +
+            '` has non-existent dependency `' +
+            dependencyName +
+            '` in ' +
+            task.join(', ');
+          throw new Error(msg);
+        }
+        var taskListeners = listeners[dependencyName];
+        if (!taskListeners) {
+          taskListeners = listeners[dependencyName] = [];
+        }
+        taskListeners.push(taskListener);
+      }
+
+      function done(err, arg) {
+        if (key === null) {
+          throwError();
+        }
+        arg = arguments.length <= 2 ? arg : slice(arguments, 1);
+        if (err) {
+          rest = 0;
+          runningTasks = 0;
+          readyTasks.length = 0;
+          var safeResults = objectClone(results);
+          safeResults[key] = arg;
+          key = null;
+          var _callback = callback;
+          callback = noop;
+          _callback(err, safeResults);
+          return;
+        }
+        runningTasks--;
+        rest--;
+        results[key] = arg;
+        taskComplete(key);
+        key = null;
+      }
+
+      function taskListener() {
+        if (--dependencySize === 0) {
+          readyTasks.push([_task, _taskSize, done]);
+        }
+      }
+    }
+
+    function proceedQueue() {
+      if (readyTasks.length === 0 && runningTasks === 0) {
+        if (rest !== 0) {
+          throw new Error('async.auto task has cyclic dependencies');
+        }
+        return callback(null, results);
+      }
+      while (readyTasks.length && runningTasks < concurrency && callback !== noop) {
+        runningTasks++;
+        var array = readyTasks.shift();
+        if (array[1] === 0) {
+          array[0](array[2]);
+        } else {
+          array[0](results, array[2]);
+        }
+      }
+    }
+
+    function taskComplete(key) {
+      var taskListeners = listeners[key] || [];
+      arrayEachSync(taskListeners, function(task) {
+        task();
+      });
+      proceedQueue();
+    }
+  }
+
+  var FN_ARGS = /^(function)?\s*[^\(]*\(\s*([^\)]*)\)/m;
+  var FN_ARG_SPLIT = /,/;
+  var FN_ARG = /(=.+)?(\s*)$/;
+  var STRIP_COMMENTS = /((\/\/.*$)|(\/\*[\s\S]*?\*\/))/gm;
+
+  /**
+   * parse function arguments for `autoInject`
+   *
+   * @private
+   */
+  function parseParams(func) {
+    func = func.toString().replace(STRIP_COMMENTS, '');
+    func = func.match(FN_ARGS)[2].replace(' ', '');
+    func = func ? func.split(FN_ARG_SPLIT) : [];
+    func = func.map(function(arg) {
+      return arg.replace(FN_ARG, '').trim();
+    });
+    return func;
+  }
+
+  /**
+   * @memberof async
+   * @namespace autoInject
+   * @param {Object} tasks
+   * @param {number} [concurrency]
+   * @param {Function} [callback]
+   */
+  function autoInject(tasks, concurrency, callback) {
+    var newTasks = {};
+    baseEachSync(tasks, iterator, nativeKeys(tasks));
+    auto(newTasks, concurrency, callback);
+
+    function iterator(task, key) {
+      var params;
+      var taskLength = task.length;
+
+      if (isArray(task)) {
+        if (taskLength === 0) {
+          throw new Error('autoInject task functions require explicit parameters.');
+        }
+        params = createArray(task);
+        taskLength = params.length - 1;
+        task = params[taskLength];
+        if (taskLength === 0) {
+          newTasks[key] = task;
+          return;
+        }
+      } else if (taskLength === 1) {
+        newTasks[key] = task;
+        return;
+      } else {
+        params = parseParams(task);
+        if (taskLength === 0 && params.length === 0) {
+          throw new Error('autoInject task functions require explicit parameters.');
+        }
+        taskLength = params.length - 1;
+      }
+      params[taskLength] = newTask;
+      newTasks[key] = params;
+
+      function newTask(results, done) {
+        switch (taskLength) {
+          case 1:
+            task(results[params[0]], done);
+            break;
+          case 2:
+            task(results[params[0]], results[params[1]], done);
+            break;
+          case 3:
+            task(results[params[0]], results[params[1]], results[params[2]], done);
+            break;
+          default:
+            var i = -1;
+            while (++i < taskLength) {
+              params[i] = results[params[i]];
+            }
+            params[i] = done;
+            task.apply(null, params);
+            break;
+        }
+      }
+    }
+  }
+
+  /**
+   * @memberof async
+   * @namespace retry
+   * @param {integer|Object|Function} opts
+   * @param {Function} [task]
+   * @param {Function} [callback]
+   */
+  function retry(opts, task, callback) {
+    var times, intervalFunc, errorFilter;
+    var count = 0;
+    if (arguments.length < 3 && typeof opts === func) {
+      callback = task || noop;
+      task = opts;
+      opts = null;
+      times = DEFAULT_TIMES;
+    } else {
+      callback = callback || noop;
+      switch (typeof opts) {
+        case 'object':
+          if (typeof opts.errorFilter === func) {
+            errorFilter = opts.errorFilter;
+          }
+          var interval = opts.interval;
+          switch (typeof interval) {
+            case func:
+              intervalFunc = interval;
+              break;
+            case 'string':
+            case 'number':
+              interval = +interval;
+              intervalFunc = interval
+                ? function() {
+                    return interval;
+                  }
+                : function() {
+                    return DEFAULT_INTERVAL;
+                  };
+              break;
+          }
+          times = +opts.times || DEFAULT_TIMES;
+          break;
+        case 'number':
+          times = opts || DEFAULT_TIMES;
+          break;
+        case 'string':
+          times = +opts || DEFAULT_TIMES;
+          break;
+        default:
+          throw new Error('Invalid arguments for async.retry');
+      }
+    }
+    if (typeof task !== 'function') {
+      throw new Error('Invalid arguments for async.retry');
+    }
+
+    if (intervalFunc) {
+      task(intervalCallback);
+    } else {
+      task(simpleCallback);
+    }
+
+    function simpleIterator() {
+      task(simpleCallback);
+    }
+
+    function simpleCallback(err, res) {
+      if (++count === times || !err || (errorFilter && !errorFilter(err))) {
+        if (arguments.length <= 2) {
+          return callback(err, res);
+        }
+        var args = createArray(arguments);
+        return callback.apply(null, args);
+      }
+      simpleIterator();
+    }
+
+    function intervalIterator() {
+      task(intervalCallback);
+    }
+
+    function intervalCallback(err, res) {
+      if (++count === times || !err || (errorFilter && !errorFilter(err))) {
+        if (arguments.length <= 2) {
+          return callback(err, res);
+        }
+        var args = createArray(arguments);
+        return callback.apply(null, args);
+      }
+      setTimeout(intervalIterator, intervalFunc(count));
+    }
+  }
+
+  function retryable(opts, task) {
+    if (!task) {
+      task = opts;
+      opts = null;
+    }
+    return done;
+
+    function done() {
+      var taskFn;
+      var args = createArray(arguments);
+      var lastIndex = args.length - 1;
+      var callback = args[lastIndex];
+      switch (task.length) {
+        case 1:
+          taskFn = task1;
+          break;
+        case 2:
+          taskFn = task2;
+          break;
+        case 3:
+          taskFn = task3;
+          break;
+        default:
+          taskFn = task4;
+      }
+      if (opts) {
+        retry(opts, taskFn, callback);
+      } else {
+        retry(taskFn, callback);
+      }
+
+      function task1(done) {
+        task(done);
+      }
+
+      function task2(done) {
+        task(args[0], done);
+      }
+
+      function task3(done) {
+        task(args[0], args[1], done);
+      }
+
+      function task4(callback) {
+        args[lastIndex] = callback;
+        task.apply(null, args);
+      }
+    }
+  }
+
+  /**
+   * @memberof async
+   * @namespace iterator
+   */
+  function iterator(tasks) {
+    var size = 0;
+    var keys = [];
+    if (isArray(tasks)) {
+      size = tasks.length;
+    } else {
+      keys = nativeKeys(tasks);
+      size = keys.length;
+    }
+    return makeCallback(0);
+
+    function makeCallback(index) {
+      var fn = function() {
+        if (size) {
+          var key = keys[index] || index;
+          tasks[key].apply(null, createArray(arguments));
+        }
+        return fn.next();
+      };
+      fn.next = function() {
+        return index < size - 1 ? makeCallback(index + 1) : null;
+      };
+      return fn;
+    }
+  }
+
+  /**
+   * @memberof async
+   * @namespace apply
+   */
+  function apply(func) {
+    switch (arguments.length) {
+      case 0:
+      case 1:
+        return func;
+      case 2:
+        return func.bind(null, arguments[1]);
+      case 3:
+        return func.bind(null, arguments[1], arguments[2]);
+      case 4:
+        return func.bind(null, arguments[1], arguments[2], arguments[3]);
+      case 5:
+        return func.bind(null, arguments[1], arguments[2], arguments[3], arguments[4]);
+      default:
+        var size = arguments.length;
+        var index = 0;
+        var args = Array(size);
+        args[index] = null;
+        while (++index < size) {
+          args[index] = arguments[index];
+        }
+        return func.bind.apply(func, args);
+    }
+  }
+
+  /**
+   * @memberof async
+   * @namespace timeout
+   * @param {Function} func
+   * @param {number} millisec
+   * @param {*} info
+   */
+  function timeout(func, millisec, info) {
+    var callback, timer;
+    return wrappedFunc;
+
+    function wrappedFunc() {
+      timer = setTimeout(timeoutCallback, millisec);
+      var args = createArray(arguments);
+      var lastIndex = args.length - 1;
+      callback = args[lastIndex];
+      args[lastIndex] = injectedCallback;
+      simpleApply(func, args);
+    }
+
+    function timeoutCallback() {
+      var name = func.name || 'anonymous';
+      var err = new Error('Callback function "' + name + '" timed out.');
+      err.code = 'ETIMEDOUT';
+      if (info) {
+        err.info = info;
+      }
+      timer = null;
+      callback(err);
+    }
+
+    function injectedCallback() {
+      if (timer !== null) {
+        simpleApply(callback, createArray(arguments));
+        clearTimeout(timer);
+      }
+    }
+
+    function simpleApply(func, args) {
+      switch (args.length) {
+        case 0:
+          func();
+          break;
+        case 1:
+          func(args[0]);
+          break;
+        case 2:
+          func(args[0], args[1]);
+          break;
+        default:
+          func.apply(null, args);
+          break;
+      }
+    }
+  }
+
+  /**
+   * @memberof async
+   * @namespace times
+   * @param {number} n - n >= 1
+   * @param {Function} iterator
+   * @param {Function} callback
+   * @example
+   *
+   * var iterator = function(n, done) {
+   *   done(null, n);
+   * };
+   * async.times(4, iterator, function(err, res) {
+   *   console.log(res); // [0, 1, 2, 3];
+   * });
+   *
+   */
+  function times(n, iterator, callback) {
+    callback = callback || noop;
+    n = +n;
+    if (isNaN(n) || n < 1) {
+      return callback(null, []);
+    }
+    var result = Array(n);
+    timesSync(n, iterate);
+
+    function iterate(num) {
+      iterator(num, createCallback(num));
+    }
+
+    function createCallback(index) {
+      return function(err, res) {
+        if (index === null) {
+          throwError();
+        }
+        result[index] = res;
+        index = null;
+        if (err) {
+          callback(err);
+          callback = noop;
+        } else if (--n === 0) {
+          callback(null, result);
+        }
+      };
+    }
+  }
+
+  /**
+   * @memberof async
+   * @namespace timesSeries
+   * @param {number} n - n >= 1
+   * @param {Function} iterator
+   * @param {Function} callback
+   * @example
+   *
+   * var iterator = function(n, done) {
+   *   done(null, n);
+   * };
+   * async.timesSeries(4, iterator, function(err, res) {
+   *   console.log(res); // [0, 1, 2, 3];
+   * });
+   *
+   */
+  function timesSeries(n, iterator, callback) {
+    callback = callback || noop;
+    n = +n;
+    if (isNaN(n) || n < 1) {
+      return callback(null, []);
+    }
+    var result = Array(n);
+    var sync = false;
+    var completed = 0;
+    iterate();
+
+    function iterate() {
+      iterator(completed, done);
+    }
+
+    function done(err, res) {
+      result[completed] = res;
+      if (err) {
+        callback(err);
+        callback = throwError;
+      } else if (++completed >= n) {
+        callback(null, result);
+        callback = throwError;
+      } else if (sync) {
+        nextTick(iterate);
+      } else {
+        sync = true;
+        iterate();
+      }
+      sync = false;
+    }
+  }
+
+  /**
+   * @memberof async
+   * @namespace timesLimit
+   * @param {number} n - n >= 1
+   * @param {number} limit - n >= 1
+   * @param {Function} iterator
+   * @param {Function} callback
+   * @example
+   *
+   * var iterator = function(n, done) {
+   *   done(null, n);
+   * };
+   * async.timesLimit(4, 2, iterator, function(err, res) {
+   *   console.log(res); // [0, 1, 2, 3];
+   * });
+   *
+   */
+  function timesLimit(n, limit, iterator, callback) {
+    callback = callback || noop;
+    n = +n;
+    if (isNaN(n) || n < 1 || isNaN(limit) || limit < 1) {
+      return callback(null, []);
+    }
+    var result = Array(n);
+    var sync = false;
+    var started = 0;
+    var completed = 0;
+    timesSync(limit > n ? n : limit, iterate);
+
+    function iterate() {
+      var index = started++;
+      if (index < n) {
+        iterator(index, createCallback(index));
+      }
+    }
+
+    function createCallback(index) {
+      return function(err, res) {
+        if (index === null) {
+          throwError();
+        }
+        result[index] = res;
+        index = null;
+        if (err) {
+          callback(err);
+          callback = noop;
+        } else if (++completed >= n) {
+          callback(null, result);
+          callback = throwError;
+        } else if (sync) {
+          nextTick(iterate);
+        } else {
+          sync = true;
+          iterate();
+        }
+        sync = false;
+      };
+    }
+  }
+
+  /**
+   * @memberof async
+   * @namespace race
+   * @param {Array|Object} tasks - functions
+   * @param {Function} callback
+   * @example
+   *
+   * // array
+   * var called = 0;
+   * var tasks = [
+   *   function(done) {
+   *     setTimeout(function() {
+   *       called++;
+   *       done(null, '1');
+   *     }, 30);
+   *   },
+   *   function(done) {
+   *     setTimeout(function() {
+   *       called++;
+   *       done(null, '2');
+   *     }, 20);
+   *   },
+   *   function(done) {
+   *     setTimeout(function() {
+   *       called++;
+   *       done(null, '3');
+   *     }, 10);
+   *   }
+   * ];
+   * async.race(tasks, function(err, res) {
+   *   console.log(res); // '3'
+   *   console.log(called); // 1
+   *   setTimeout(function() {
+   *     console.log(called); // 3
+   *   }, 50);
+   * });
+   *
+   * @example
+   *
+   * // object
+   * var called = 0;
+   * var tasks = {
+   *   'test1': function(done) {
+   *     setTimeout(function() {
+   *       called++;
+   *       done(null, '1');
+   *     }, 30);
+   *   },
+   *   'test2': function(done) {
+   *     setTimeout(function() {
+   *       called++;
+   *       done(null, '2');
+   *     }, 20);
+   *   },
+   *   'test3': function(done) {
+   *     setTimeout(function() {
+   *       called++;
+   *       done(null, '3');
+   *     }, 10);
+   *   }
+   * };
+   * async.race(tasks, function(err, res) {
+   *   console.log(res); // '3'
+   *   console.log(called); // 1
+   *   setTimeout(function() {
+   *     console.log(called); // 3
+   *     done();
+   *   }, 50);
+   * });
+   *
+   */
+  function race(tasks, callback) {
+    callback = once(callback || noop);
+    var size, keys;
+    var index = -1;
+    if (isArray(tasks)) {
+      size = tasks.length;
+      while (++index < size) {
+        tasks[index](callback);
+      }
+    } else if (tasks && typeof tasks === obj) {
+      keys = nativeKeys(tasks);
+      size = keys.length;
+      while (++index < size) {
+        tasks[keys[index]](callback);
+      }
+    } else {
+      return callback(new TypeError('First argument to race must be a collection of functions'));
+    }
+    if (!size) {
+      callback(null);
+    }
+  }
+
+  /**
+   * @memberof async
+   * @namespace memoize
+   */
+  function memoize(fn, hasher) {
+    hasher =
+      hasher ||
+      function(hash) {
+        return hash;
+      };
+
+    var memo = {};
+    var queues = {};
+    var memoized = function() {
+      var args = createArray(arguments);
+      var callback = args.pop();
+      var key = hasher.apply(null, args);
+      if (has(memo, key)) {
+        nextTick(function() {
+          callback.apply(null, memo[key]);
+        });
+        return;
+      }
+      if (has(queues, key)) {
+        return queues[key].push(callback);
+      }
+
+      queues[key] = [callback];
+      args.push(done);
+      fn.apply(null, args);
+
+      function done(err) {
+        var args = createArray(arguments);
+        if (!err) {
+          memo[key] = args;
+        }
+        var q = queues[key];
+        delete queues[key];
+
+        var i = -1;
+        var size = q.length;
+        while (++i < size) {
+          q[i].apply(null, args);
+        }
+      }
+    };
+    memoized.memo = memo;
+    memoized.unmemoized = fn;
+    return memoized;
+  }
+
+  /**
+   * @memberof async
+   * @namespace unmemoize
+   */
+  function unmemoize(fn) {
+    return function() {
+      return (fn.unmemoized || fn).apply(null, arguments);
+    };
+  }
+
+  /**
+   * @memberof async
+   * @namespace ensureAsync
+   */
+  function ensureAsync(fn) {
+    return function(/* ...args, callback */) {
+      var args = createArray(arguments);
+      var lastIndex = args.length - 1;
+      var callback = args[lastIndex];
+      var sync = true;
+      args[lastIndex] = done;
+      fn.apply(this, args);
+      sync = false;
+
+      function done() {
+        var innerArgs = createArray(arguments);
+        if (sync) {
+          nextTick(function() {
+            callback.apply(null, innerArgs);
+          });
+        } else {
+          callback.apply(null, innerArgs);
+        }
+      }
+    };
+  }
+
+  /**
+   * @memberof async
+   * @namespace constant
+   */
+  function constant(/* values... */) {
+    var args = [null].concat(createArray(arguments));
+    return function(callback) {
+      callback = arguments[arguments.length - 1];
+      callback.apply(this, args);
+    };
+  }
+
+  function asyncify(fn) {
+    return function(/* args..., callback */) {
+      var args = createArray(arguments);
+      var callback = args.pop();
+      var result;
+      try {
+        result = fn.apply(this, args);
+      } catch (e) {
+        return callback(e);
+      }
+      if (result && typeof result.then === func) {
+        result.then(
+          function(value) {
+            invokeCallback(callback, null, value);
+          },
+          function(err) {
+            invokeCallback(callback, err && err.message ? err : new Error(err));
+          }
+        );
+      } else {
+        callback(null, result);
+      }
+    };
+  }
+
+  function invokeCallback(callback, err, value) {
+    try {
+      callback(err, value);
+    } catch (e) {
+      nextTick(rethrow, e);
+    }
+  }
+
+  function rethrow(error) {
+    throw error;
+  }
+
+  /**
+   * @memberof async
+   * @namespace reflect
+   * @param {Function} func
+   * @return {Function}
+   */
+  function reflect(func) {
+    return function(/* args..., callback */) {
+      var callback;
+      switch (arguments.length) {
+        case 1:
+          callback = arguments[0];
+          return func(done);
+        case 2:
+          callback = arguments[1];
+          return func(arguments[0], done);
+        default:
+          var args = createArray(arguments);
+          var lastIndex = args.length - 1;
+          callback = args[lastIndex];
+          args[lastIndex] = done;
+          func.apply(this, args);
+      }
+
+      function done(err, res) {
+        if (err) {
+          return callback(null, {
+            error: err
+          });
+        }
+        if (arguments.length > 2) {
+          res = slice(arguments, 1);
+        }
+        callback(null, {
+          value: res
+        });
+      }
+    };
+  }
+
+  /**
+   * @memberof async
+   * @namespace reflectAll
+   * @param {Array[]|Object} tasks
+   * @return {Function}
+   */
+  function reflectAll(tasks) {
+    var newTasks, keys;
+    if (isArray(tasks)) {
+      newTasks = Array(tasks.length);
+      arrayEachSync(tasks, iterate);
+    } else if (tasks && typeof tasks === obj) {
+      keys = nativeKeys(tasks);
+      newTasks = {};
+      baseEachSync(tasks, iterate, keys);
+    }
+    return newTasks;
+
+    function iterate(func, key) {
+      newTasks[key] = reflect(func);
+    }
+  }
+
+  /**
+   * @memberof async
+   * @namespace createLogger
+   */
+  function createLogger(name) {
+    return function(fn) {
+      var args = slice(arguments, 1);
+      args.push(done);
+      fn.apply(null, args);
+    };
+
+    function done(err) {
+      if (typeof console === obj) {
+        if (err) {
+          if (console.error) {
+            console.error(err);
+          }
+          return;
+        }
+        if (console[name]) {
+          var args = slice(arguments, 1);
+          arrayEachSync(args, function(arg) {
+            console[name](arg);
+          });
+        }
+      }
+    }
+  }
+
+  /**
+   * @memberof async
+   * @namespace safe
+   */
+  function safe() {
+    createImmediate();
+    return exports;
+  }
+
+  /**
+   * @memberof async
+   * @namespace fast
+   */
+  function fast() {
+    createImmediate(false);
+    return exports;
+  }
+});
