1'use strict';
 2/* eslint-disable no-unused-vars */
 3var hasOwnProperty = Object.prototype.hasOwnProperty;
 4var propIsEnumerable = Object.prototype.propertyIsEnumerable;
 5
 6function toObject(val) {
 7	if (val === null || val === undefined) {
 8		throw new TypeError('Object.assign cannot be called with null or undefined');
 9	}
10
11	return Object(val);
12}
13
14function shouldUseNative() {
15	try {
16		if (!Object.assign) {
17			return false;
18		}
19
20		// Detect buggy property enumeration order in older V8 versions.
21
22		// https://bugs.chromium.org/p/v8/issues/detail?id=4118
23		var test1 = new String('abc');  // eslint-disable-line
24		test1[5] = 'de';
25		if (Object.getOwnPropertyNames(test1)[0] === '5') {
26			return false;
27		}
28
29		// https://bugs.chromium.org/p/v8/issues/detail?id=3056
30		var test2 = {};
31		for (var i = 0; i < 10; i++) {
32			test2['_' + String.fromCharCode(i)] = i;
33		}
34		var order2 = Object.getOwnPropertyNames(test2).map(function (n) {
35			return test2[n];
36		});
37		if (order2.join('') !== '0123456789') {
38			return false;
39		}
40
41		// https://bugs.chromium.org/p/v8/issues/detail?id=3056
42		var test3 = {};
43		'abcdefghijklmnopqrst'.split('').forEach(function (letter) {
44			test3[letter] = letter;
45		});
46		if (Object.keys(Object.assign({}, test3)).join('') !==
47				'abcdefghijklmnopqrst') {
48			return false;
49		}
50
51		return true;
52	} catch (e) {
53		// We don't expect any of the above to throw, but better to be safe.
54		return false;
55	}
56}
57
58module.exports = shouldUseNative() ? Object.assign : function (target, source) {
59	var from;
60	var to = toObject(target);
61	var symbols;
62
63	for (var s = 1; s < arguments.length; s++) {
64		from = Object(arguments[s]);
65
66		for (var key in from) {
67			if (hasOwnProperty.call(from, key)) {
68				to[key] = from[key];
69			}
70		}
71
72		if (Object.getOwnPropertySymbols) {
73			symbols = Object.getOwnPropertySymbols(from);
74			for (var i = 0; i < symbols.length; i++) {
75				if (propIsEnumerable.call(from, symbols[i])) {
76					to[symbols[i]] = from[symbols[i]];
77				}
78			}
79		}
80	}
81
82	return to;
83};