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30-seconds-of-code/snippets/all.md
Mathias Bynens 8ee50178f3 Avoid confusing prototype methods for static methods
Correct: `Array.from()` (it’s a static method)
Incorrect: `Array.join()` (doesn’t exist; it’s a prototype method)

This patch uses the common `#` syntax to denote `.prototype.`.
2018-09-28 15:44:12 -04:00

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### all
Returns `true` if the provided predicate function returns `true` for all elements in a collection, `false` otherwise.
Use `Array.prototype.every()` to test if all elements in the collection return `true` based on `fn`.
Omit the second argument, `fn`, to use `Boolean` as a default.
```js
const all = (arr, fn = Boolean) => arr.every(fn);
```
```js
all([4, 2, 3], x => x > 1); // true
all([1, 2, 3]); // true
```