source: node_modules/object-assign/index.js@ 47f4eaf

/*
object-assign
(c) Sindre Sorhus
@license MIT
*/

'use strict';
/* eslint-disable no-unused-vars */
var getOwnPropertySymbols = Object.getOwnPropertySymbols;
var hasOwnProperty = Object.prototype.hasOwnProperty;
var propIsEnumerable = Object.prototype.propertyIsEnumerable;

function toObject(val) {
        if (val === null || val === undefined) {
                throw new TypeError('Object.assign cannot be called with null or undefined');
        }

        return Object(val);
}

function shouldUseNative() {
        try {
                if (!Object.assign) {
                        return false;
                }

                // Detect buggy property enumeration order in older V8 versions.

                // https://bugs.chromium.org/p/v8/issues/detail?id=4118
                var test1 = new String('abc');  // eslint-disable-line no-new-wrappers
                test1[5] = 'de';
                if (Object.getOwnPropertyNames(test1)[0] === '5') {
                        return false;
                }

                // https://bugs.chromium.org/p/v8/issues/detail?id=3056
                var test2 = {};
                for (var i = 0; i < 10; i++) {
                        test2['_' + String.fromCharCode(i)] = i;
                }
                var order2 = Object.getOwnPropertyNames(test2).map(function (n) {
                        return test2[n];
                });
                if (order2.join('') !== '0123456789') {
                        return false;
                }

                // https://bugs.chromium.org/p/v8/issues/detail?id=3056
                var test3 = {};
                'abcdefghijklmnopqrst'.split('').forEach(function (letter) {
                        test3[letter] = letter;
                });
                if (Object.keys(Object.assign({}, test3)).join('') !==
                                'abcdefghijklmnopqrst') {
                        return false;
                }

                return true;
        } catch (err) {
                // We don't expect any of the above to throw, but better to be safe.
                return false;
        }
}

module.exports = shouldUseNative() ? Object.assign : function (target, source) {
        var from;
        var to = toObject(target);
        var symbols;

        for (var s = 1; s < arguments.length; s++) {
                from = Object(arguments[s]);

                for (var key in from) {
                        if (hasOwnProperty.call(from, key)) {
                                to[key] = from[key];
                        }
                }

                if (getOwnPropertySymbols) {
                        symbols = getOwnPropertySymbols(from);
                        for (var i = 0; i < symbols.length; i++) {
                                if (propIsEnumerable.call(from, symbols[i])) {
                                        to[symbols[i]] = from[symbols[i]];
                                }
                        }
                }
        }

        return to;
};