59 lines
1.6 KiB
Plaintext
59 lines
1.6 KiB
Plaintext
// @flow strict
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import { SYMBOL_ITERATOR } from './symbols';
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declare function arrayFrom<T>(arrayLike: Iterable<T>): Array<T>;
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// eslint-disable-next-line no-redeclare
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declare function arrayFrom<T: mixed>(
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arrayLike: mixed,
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mapFn?: (elem: mixed, index: number) => T,
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thisArg?: mixed,
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): Array<T>;
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/* eslint-disable no-redeclare */
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// $FlowFixMe[name-already-bound]
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const arrayFrom =
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Array.from ||
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function (obj, mapFn, thisArg) {
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if (obj == null) {
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throw new TypeError(
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'Array.from requires an array-like object - not null or undefined',
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);
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}
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// Is Iterable?
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const iteratorMethod = obj[SYMBOL_ITERATOR];
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if (typeof iteratorMethod === 'function') {
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const iterator = iteratorMethod.call(obj);
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const result = [];
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let step;
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for (let i = 0; !(step = iterator.next()).done; ++i) {
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result.push(mapFn.call(thisArg, step.value, i));
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// Infinite Iterators could cause forEach to run forever.
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// After a very large number of iterations, produce an error.
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// istanbul ignore if (Too big to actually test)
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if (i > 9999999) {
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throw new TypeError('Near-infinite iteration.');
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}
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}
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return result;
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}
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// Is Array like?
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const length = obj.length;
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if (typeof length === 'number' && length >= 0 && length % 1 === 0) {
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const result = [];
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for (let i = 0; i < length; ++i) {
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if (Object.prototype.hasOwnProperty.call(obj, i)) {
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result.push(mapFn.call(thisArg, obj[i], i));
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}
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}
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return result;
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}
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return [];
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};
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export default arrayFrom;
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