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// |reftest| shell-option(--enable-iterator-helpers) skip-if(!this.hasOwnProperty('Iterator')||!xulRuntime.shell) -- iterator-helpers is not enabled unconditionally, requires shell-options
// Copyright (C) 2023 Michael Ficarra. All rights reserved.
// This code is governed by the BSD license found in the LICENSE file.
/*---
esid: sec-iterator.from
description: >
Gets the next method from the underlying iterator only once
info: |
Iterator.from ( O )
2. Let iteratorRecord be ? GetIteratorFlattenable(O).
features: [iterator-helpers]
flags: []
---*/
let nextGets = 0;
let nextCalls = 0;
class CountingIterator {
get next() {
++nextGets;
let iter = (function* () {
for (let i = 1; i < 5; ++i) {
yield i;
}
})();
return function () {
++nextCalls;
return iter.next();
};
}
}
let iterator = new CountingIterator();
assert.sameValue(nextGets, 0, 'The value of `nextGets` is 0');
assert.sameValue(nextCalls, 0, 'The value of `nextCalls` is 0');
iterator = Iterator.from(iterator);
assert.sameValue(nextGets, 1, 'The value of `nextGets` is 1');
assert.sameValue(nextCalls, 0, 'The value of `nextCalls` is 0');
iterator.toArray();
assert.sameValue(nextGets, 1, 'The value of `nextGets` is 1');
assert.sameValue(nextCalls, 5, 'The value of `nextCalls` is 5');
reportCompare(0, 0);