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47 lines
2.0 KiB
47 lines
2.0 KiB
4 weeks ago
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'use strict';
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var bind = require('../internals/function-bind-context');
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var call = require('../internals/function-call');
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var toObject = require('../internals/to-object');
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var callWithSafeIterationClosing = require('../internals/call-with-safe-iteration-closing');
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var isArrayIteratorMethod = require('../internals/is-array-iterator-method');
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var isConstructor = require('../internals/is-constructor');
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var lengthOfArrayLike = require('../internals/length-of-array-like');
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var createProperty = require('../internals/create-property');
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var getIterator = require('../internals/get-iterator');
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var getIteratorMethod = require('../internals/get-iterator-method');
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var $Array = Array;
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// `Array.from` method implementation
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// https://tc39.es/ecma262/#sec-array.from
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module.exports = function from(arrayLike /* , mapfn = undefined, thisArg = undefined */) {
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var O = toObject(arrayLike);
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var IS_CONSTRUCTOR = isConstructor(this);
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var argumentsLength = arguments.length;
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var mapfn = argumentsLength > 1 ? arguments[1] : undefined;
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var mapping = mapfn !== undefined;
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if (mapping) mapfn = bind(mapfn, argumentsLength > 2 ? arguments[2] : undefined);
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var iteratorMethod = getIteratorMethod(O);
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var index = 0;
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var length, result, step, iterator, next, value;
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// if the target is not iterable or it's an array with the default iterator - use a simple case
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if (iteratorMethod && !(this === $Array && isArrayIteratorMethod(iteratorMethod))) {
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result = IS_CONSTRUCTOR ? new this() : [];
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iterator = getIterator(O, iteratorMethod);
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next = iterator.next;
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for (;!(step = call(next, iterator)).done; index++) {
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value = mapping ? callWithSafeIterationClosing(iterator, mapfn, [step.value, index], true) : step.value;
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createProperty(result, index, value);
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}
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} else {
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length = lengthOfArrayLike(O);
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result = IS_CONSTRUCTOR ? new this(length) : $Array(length);
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for (;length > index; index++) {
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value = mapping ? mapfn(O[index], index) : O[index];
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createProperty(result, index, value);
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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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