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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*<br>
Type: `number`
The maximum number of items before evicting the least recently used items.
### 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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