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30-seconds-of-code/snippets/partition.md
Angelos Chalaris 481fe3c937 Update partition.md
2018-01-08 17:28:00 +02:00

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### partition
Groups the elements into two arrays, depending on the provided function's truthiness for each element.
Use `Array.reduce()` to create an array of two arrays.
Use `Array.push()` to add elements for which `fn` returns `true` to the first array and elements for which `fn` returns `false` to the second one.
```js
const partition = (arr, fn) =>
arr.reduce((acc, val, i, arr) => {acc[fn(val,i,arr) ? 0 :1].push(val); return acc;},[[],[]]);
```
```js
var users = [
{ 'user': 'barney', 'age': 36, 'active': false },
{ 'user': 'fred', 'age': 40, 'active': true }
];
partition(users, o => o.active) // [[{ 'user': 'fred', 'age': 40, 'active': true }],[{ 'user': 'barney', 'age': 36, 'active': false }]]
```