21 lines
509 B
Markdown
21 lines
509 B
Markdown
---
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title: all
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tags: array,beginner
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firstSeen: 2018-02-14T11:46:15+02:00
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lastUpdated: 2020-10-18T20:24:28+03:00
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---
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Checks if the provided predicate function returns `true` for all elements in a collection.
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- Use `Array.prototype.every()` to test if all elements in the collection return `true` based on `fn`.
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- Omit the second argument, `fn`, to use `Boolean` as a default.
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```js
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const all = (arr, fn = Boolean) => arr.every(fn);
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```
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```js
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all([4, 2, 3], x => x > 1); // true
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all([1, 2, 3]); // true
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```
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