lru

A simple LRU cache supporting O(1) set, get and eviction of old keys

Installation

$ npm install lru

Example

var LRU = require('lru');

var cache = new LRU(2),
    evicted

cache.on('evict',function(data) { evicted = data });

cache.set('foo', 'bar');
cache.get('foo'); //=> bar

cache.set('foo2', 'bar2');
cache.get('foo2'); //=> bar2

cache.set('foo3', 'bar3'); // => evicted = { key: 'foo', value: 'bar' }
cache.get('foo3');         // => 'bar3'
cache.remove('foo2')       // => 'bar2'
cache.remove('foo4')       // => undefined
cache.length               // => 1
cache.keys                 // => ['foo3']

cache.clear()              // => it will NOT emit the 'evict' event
cache.length               // => 0
cache.keys                 // => []

API

LRU( length )

Create a new LRU cache that stores length elements before evicting the least recently used. Optionally you can pass an options map with additional options:

{
  max: maxElementsToStore,
  maxAge: maxAgeInMilliseconds
}

If you pass maxAge items will be evicted if they are older than maxAge when you access them.

Returns: the newly created LRU cache

Properties

.length

The number of keys currently in the cache.

.keys

Array of all the keys currently in the cache.

Methods

.set( key, value )

Set the value of the key and mark the key as most recently used.

Returns: value

.get( key )

Query the value of the key and mark the key as most recently used.

Returns: value of key if found; undefined otherwise.

.peek( key )

Query the value of the key without marking the key as most recently used.

Returns: value of key if found; undefined otherwise.

.remove( key )

Remove the value from the cache.

Returns: value of key if found; undefined otherwise.

.clear()

Clear the cache. This method does NOT emit the evict event.

.on( event, callback )

Respond to events. Currently only the evict event is implemented. When a key is evicted, the callback is executed with an associative array containing the evicted key: {key: key, value: value}.

Credits

A big thanks to Dusty Leary who finished the library.

License

MIT