84 lines
1.9 KiB
JavaScript
84 lines
1.9 KiB
JavaScript
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'use strict';
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/* eslint-disable no-unused-vars */
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var hasOwnProperty = Object.prototype.hasOwnProperty;
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var propIsEnumerable = Object.prototype.propertyIsEnumerable;
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function toObject(val) {
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if (val === null || val === undefined) {
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throw new TypeError('Object.assign cannot be called with null or undefined');
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}
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return Object(val);
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}
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function shouldUseNative() {
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try {
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if (!Object.assign) {
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return false;
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}
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// Detect buggy property enumeration order in older V8 versions.
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// https://bugs.chromium.org/p/v8/issues/detail?id=4118
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var test1 = new String('abc'); // eslint-disable-line
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test1[5] = 'de';
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if (Object.getOwnPropertyNames(test1)[0] === '5') {
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return false;
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}
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// https://bugs.chromium.org/p/v8/issues/detail?id=3056
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var test2 = {};
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for (var i = 0; i < 10; i++) {
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test2['_' + String.fromCharCode(i)] = i;
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}
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var order2 = Object.getOwnPropertyNames(test2).map(function (n) {
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return test2[n];
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});
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if (order2.join('') !== '0123456789') {
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return false;
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}
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// https://bugs.chromium.org/p/v8/issues/detail?id=3056
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var test3 = {};
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'abcdefghijklmnopqrst'.split('').forEach(function (letter) {
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test3[letter] = letter;
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});
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if (Object.keys(Object.assign({}, test3)).join('') !==
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'abcdefghijklmnopqrst') {
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return false;
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}
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return true;
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} catch (e) {
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// We don't expect any of the above to throw, but better to be safe.
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return false;
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}
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}
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module.exports = shouldUseNative() ? Object.assign : function (target, source) {
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var from;
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var to = toObject(target);
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var symbols;
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for (var s = 1; s < arguments.length; s++) {
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from = Object(arguments[s]);
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for (var key in from) {
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if (hasOwnProperty.call(from, key)) {
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to[key] = from[key];
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}
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}
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if (Object.getOwnPropertySymbols) {
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symbols = Object.getOwnPropertySymbols(from);
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for (var i = 0; i < symbols.length; i++) {
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if (propIsEnumerable.call(from, symbols[i])) {
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to[symbols[i]] = from[symbols[i]];
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}
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}
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}
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}
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return to;
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};
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