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1'use strict';
2var bind = require('../internals/function-bind-context');
3var call = require('../internals/function-call');
4var toObject = require('../internals/to-object');
5var callWithSafeIterationClosing = require('../internals/call-with-safe-iteration-closing');
6var isArrayIteratorMethod = require('../internals/is-array-iterator-method');
7var isConstructor = require('../internals/is-constructor');
8var lengthOfArrayLike = require('../internals/length-of-array-like');
9var createProperty = require('../internals/create-property');
10var getIterator = require('../internals/get-iterator');
11var getIteratorMethod = require('../internals/get-iterator-method');
12
13var $Array = Array;
14
15// `Array.from` method implementation
16// https://tc39.es/ecma262/#sec-array.from
17module.exports = function from(arrayLike /* , mapfn = undefined, thisArg = undefined */) {
18 var O = toObject(arrayLike);
19 var IS_CONSTRUCTOR = isConstructor(this);
20 var argumentsLength = arguments.length;
21 var mapfn = argumentsLength > 1 ? arguments[1] : undefined;
22 var mapping = mapfn !== undefined;
23 if (mapping) mapfn = bind(mapfn, argumentsLength > 2 ? arguments[2] : undefined);
24 var iteratorMethod = getIteratorMethod(O);
25 var index = 0;
26 var length, result, step, iterator, next, value;
27 // if the target is not iterable or it's an array with the default iterator - use a simple case
28 if (iteratorMethod && !(this === $Array && isArrayIteratorMethod(iteratorMethod))) {
29 result = IS_CONSTRUCTOR ? new this() : [];
30 iterator = getIterator(O, iteratorMethod);
31 next = iterator.next;
32 for (;!(step = call(next, iterator)).done; index++) {
33 value = mapping ? callWithSafeIterationClosing(iterator, mapfn, [step.value, index], true) : step.value;
34 createProperty(result, index, value);
35 }
36 } else {
37 length = lengthOfArrayLike(O);
38 result = IS_CONSTRUCTOR ? new this(length) : $Array(length);
39 for (;length > index; index++) {
40 value = mapping ? mapfn(O[index], index) : O[index];
41 createProperty(result, index, value);
42 }
43 }
44 result.length = index;
45 return result;
46};