source: imaps-frontend/node_modules/object.assign/polyfill.js@ d565449

'use strict';

var implementation = require('./implementation');

var lacksProperEnumerationOrder = function () {
        if (!Object.assign) {
                return false;
        }
        /*
         * v8, specifically in node 4.x, has a bug with incorrect property enumeration order
         * note: this does not detect the bug unless there's 20 characters
         */
        var str = 'abcdefghijklmnopqrst';
        var letters = str.split('');
        var map = {};
        for (var i = 0; i < letters.length; ++i) {
                map[letters[i]] = letters[i];
        }
        var obj = Object.assign({}, map);
        var actual = '';
        for (var k in obj) {
                actual += k;
        }
        return str !== actual;
};

var assignHasPendingExceptions = function () {
        if (!Object.assign || !Object.preventExtensions) {
                return false;
        }
        /*
         * Firefox 37 still has "pending exception" logic in its Object.assign implementation,
         * which is 72% slower than our shim, and Firefox 40's native implementation.
         */
        var thrower = Object.preventExtensions({ 1: 2 });
        try {
                Object.assign(thrower, 'xy');
        } catch (e) {
                return thrower[1] === 'y';
        }
        return false;
};

module.exports = function getPolyfill() {
        if (!Object.assign) {
                return implementation;
        }
        if (lacksProperEnumerationOrder()) {
                return implementation;
        }
        if (assignHasPendingExceptions()) {
                return implementation;
        }
        return Object.assign;
};