react-native/Libraries/polyfills/Array.es6.js

87 lines
1.7 KiB
JavaScript

/**
* Copyright (c) 2013-present, Facebook, Inc.
*
* This source code is licensed under the MIT license found in the
* LICENSE file in the root directory of this source tree.
*
* @providesModule Array.es6
* @polyfill
* @nolint
*/
/* eslint-disable consistent-this */
/**
* Creates an array from array like objects.
*
* https://people.mozilla.org/~jorendorff/es6-draft.html#sec-array.from
*/
if (!Array.from) {
Array.from = function(arrayLike /*, mapFn, thisArg */) {
if (arrayLike == null) {
throw new TypeError('Object is null or undefined');
}
// Optional args.
var mapFn = arguments[1];
var thisArg = arguments[2];
var C = this;
var items = Object(arrayLike);
var symbolIterator = typeof Symbol === 'function'
? Symbol.iterator
: '@@iterator';
var mapping = typeof mapFn === 'function';
var usingIterator = typeof items[symbolIterator] === 'function';
var key = 0;
var ret;
var value;
if (usingIterator) {
ret = typeof C === 'function'
? new C()
: [];
var it = items[symbolIterator]();
var next;
while (!(next = it.next()).done) {
value = next.value;
if (mapping) {
value = mapFn.call(thisArg, value, key);
}
ret[key] = value;
key += 1;
}
ret.length = key;
return ret;
}
var len = items.length;
if (isNaN(len) || len < 0) {
len = 0;
}
ret = typeof C === 'function'
? new C(len)
: new Array(len);
while (key < len) {
value = items[key];
if (mapping) {
value = mapFn.call(thisArg, value, key);
}
ret[key] = value;
key += 1;
}
ret.length = key;
return ret;
};
}