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# quick-lru [](https://travis-ci.org/sindresorhus/quick-lru) [](https://coveralls.io/github/sindresorhus/quick-lru?branch=master) | |
> Simple [“Least Recently Used” (LRU) cache](https://en.m.wikipedia.org/wiki/Cache_replacement_policies#Least_Recently_Used_.28LRU.29) | |
Useful when you need to cache something and limit memory usage. | |
Inspired by the [`hashlru` algorithm](https://github.com/dominictarr/hashlru#algorithm), but instead uses [`Map`](https://developer.mozilla.org/en/docs/Web/JavaScript/Reference/Global_Objects/Map) to support keys of any type, not just strings, and values can be `undefined`. | |
## Install | |
``` | |
$ npm install quick-lru | |
``` | |
## Usage | |
```js | |
const QuickLRU = require('quick-lru'); | |
const lru = new QuickLRU({maxSize: 1000}); | |
lru.set('🦄', '🌈'); | |
lru.has('🦄'); | |
//=> true | |
lru.get('🦄'); | |
//=> '🌈' | |
``` | |
## API | |
### new QuickLRU(options?) | |
Returns a new instance. | |
### options | |
Type: `object` | |
#### maxSize | |
*Required*\ | |
Type: `number` | |
The maximum number of items before evicting the least recently used items. | |
#### onEviction | |
*Optional*\ | |
Type: `(key, value) => void` | |
Called right before an item is evicted from the cache. | |
Useful for side effects or for items like object URLs that need explicit cleanup (`revokeObjectURL`). | |
### Instance | |
The instance is [`iterable`](https://developer.mozilla.org/en/docs/Web/JavaScript/Reference/Iteration_protocols) so you can use it directly in a [`for…of`](https://developer.mozilla.org/en/docs/Web/JavaScript/Reference/Statements/for...of) loop. | |
Both `key` and `value` can be of any type. | |
#### .set(key, value) | |
Set an item. Returns the instance. | |
#### .get(key) | |
Get an item. | |
#### .has(key) | |
Check if an item exists. | |
#### .peek(key) | |
Get an item without marking it as recently used. | |
#### .delete(key) | |
Delete an item. | |
Returns `true` if the item is removed or `false` if the item doesn't exist. | |
#### .clear() | |
Delete all items. | |
#### .keys() | |
Iterable for all the keys. | |
#### .values() | |
Iterable for all the values. | |
#### .size | |
The stored item count. | |
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