mirror of https://github.com/tc39/test262.git
47 lines
1.1 KiB
JavaScript
47 lines
1.1 KiB
JavaScript
// Copyright (C) 2023 Michael Ficarra. All rights reserved.
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// This code is governed by the BSD license found in the LICENSE file.
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/*---
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esid: sec-iterator.from
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description: >
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Gets the next method from the underlying iterator only once
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info: |
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Iterator.from ( O )
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2. Let iteratorRecord be ? GetIteratorFlattenable(O).
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features: [iterator-helpers]
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flags: []
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---*/
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let nextGets = 0;
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let nextCalls = 0;
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class CountingIterator {
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get next() {
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++nextGets;
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let iter = (function* () {
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for (let i = 1; i < 5; ++i) {
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yield i;
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}
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})();
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return function () {
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++nextCalls;
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return iter.next();
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};
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}
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}
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let iterator = new CountingIterator();
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assert.sameValue(nextGets, 0, 'The value of `nextGets` is 0');
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assert.sameValue(nextCalls, 0, 'The value of `nextCalls` is 0');
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iterator = Iterator.from(iterator);
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assert.sameValue(nextGets, 1, 'The value of `nextGets` is 1');
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assert.sameValue(nextCalls, 0, 'The value of `nextCalls` is 0');
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iterator.toArray();
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assert.sameValue(nextGets, 1, 'The value of `nextGets` is 1');
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assert.sameValue(nextCalls, 5, 'The value of `nextCalls` is 5');
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