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38 lines
1.6 KiB
JavaScript
38 lines
1.6 KiB
JavaScript
5 years ago
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'use strict';
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var ctx = require('./_ctx');
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var $export = require('./_export');
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var toObject = require('./_to-object');
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var call = require('./_iter-call');
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var isArrayIter = require('./_is-array-iter');
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var toLength = require('./_to-length');
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var createProperty = require('./_create-property');
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var getIterFn = require('./core.get-iterator-method');
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$export($export.S + $export.F * !require('./_iter-detect')(function (iter) { Array.from(iter); }), 'Array', {
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// 22.1.2.1 Array.from(arrayLike, mapfn = undefined, thisArg = undefined)
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from: function from(arrayLike /* , mapfn = undefined, thisArg = undefined */) {
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var O = toObject(arrayLike);
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var C = typeof this == 'function' ? this : Array;
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var aLen = arguments.length;
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var mapfn = aLen > 1 ? arguments[1] : undefined;
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var mapping = mapfn !== undefined;
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var index = 0;
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var iterFn = getIterFn(O);
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var length, result, step, iterator;
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if (mapping) mapfn = ctx(mapfn, aLen > 2 ? arguments[2] : undefined, 2);
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// if object isn't iterable or it's array with default iterator - use simple case
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if (iterFn != undefined && !(C == Array && isArrayIter(iterFn))) {
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for (iterator = iterFn.call(O), result = new C(); !(step = iterator.next()).done; index++) {
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createProperty(result, index, mapping ? call(iterator, mapfn, [step.value, index], true) : step.value);
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}
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} else {
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length = toLength(O.length);
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for (result = new C(length); length > index; index++) {
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createProperty(result, index, mapping ? mapfn(O[index], index) : O[index]);
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}
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}
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result.length = index;
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return result;
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}
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});
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