lru-cache-node

lru-cache-node

A lighting fast cache manager for node with least-recently-used policy.

A super fast cache for node with LRU policy. Cache will keep on adding values until the limit is reached.

After that it will start popping out the Least recently used/accessed value from the cache in order to set the new ones.

Supports expiry and stale gets.

Implemented using doubly-linked-list and hashmap with O(1) time complexity for gets and sets.

Install

$ npm install --save lru-cache-node

Usage

const Cache = require('lru-cache-node');

let cache = new Cache(3); //set max size of cache as three

cache.set('a', 7); //sets a value in cache with 'a' as key and 7 as value
cache.set('b', 5);
cache.set('c', 3); 
/*
  [ { key: 'c', value: 3 },
    { key: 'b', value: 5 },
    { key: 'a', value: 7 } ]
 */
 
cache.set('d', 10) // pops out a
/*
  [ { key: 'd', value: 10 },
    { key: 'c', value: 3 },
    { key: 'b', value: 5 } ]
 */
 
cache.get("b") //returns 5 and makes it most recently used
/*
  [ { key: 'b', value: 5 },
    { key: 'd', value: 10 },
    { key: 'c', value: 3 } ]
 */

cache.peek("d") //returns 10 but doesnt resets the order
/*
  [ { key: 'b', value: 5 },
    { key: 'd', value: 10 },
    { key: 'c', value: 3 } ]
 */

let cache = new Cache(3, 10); //Initialize Cache with size 3 and expiry for keys as 10ms
const sleep = ms => new Promise(r => setTimeout(r, ms));

cache.set('a', 7); //valid for 10ms
cache.get('a'); //returns 7 and resets 10ms counter
await sleep(15);
cache.get('a'); //null

cache.set('b', 5, 30); //overwrites cache's default expiry of 10ms and uses 30ms
await sleep(15);
cache.get('b'); //returns 5 and resets the expiry of b back to 30ms
await sleep(35);
cache.get('b'); //null

API

cache(maxSize, maxAge, stale)

maxSize

Type: Number
Default: Infinity

Maximum size of the cache.

maxAge

Type: Number
Default: Infinity

Default expiry for all keys for the cache. It does not proactively deletes expired keys, but will return null when an expired key is being accessed.

stale

Type: Boolean
Default: false

If set to true, will return the value of expired key before deleting it from cache.

set(key, value, maxAge)

key

Key to be set.

value

Value for the key.

maxAge

Expiry of the key. Will override cache's maxAge if specified.

get(key)

Returns the value for the key. If not key does not exist will return null.

Both set() and get() will update the "recently used"-ness and expiry of the key.

peek(key)

Returns the value for the key, without making the key most recently used. If not key does not exist will return null.

delete(key)

Deletes the key from the cache.

contains(key)

Returns a boolean indication if the value exists in cache or not.

getSize()

Returns the current size of cache.

reset()

Clears the whole cache and reinitialize it.

toArray()

Returns an array form of the catch.

let cache = new Cache();
cache.set("a", 5);
cache.set("b", 4);
cache.set("c", 0);
cache.toArray()
/*
[ { key: 'c', value: 0 },
  { key: 'b', value: 4 },
  { key: 'a', value: 5 } ]
*/

forEach(callback)

Takes a function and iterates over all the keys in the cache, in order of recent-ness. Callback takes key, value and index as params.

let cache = new Cache();
cache.set("a", 1);
cache.set("b", 2);
cache.set("c", 3);
cache.forEach((key, value, index) => {
	console.log(key, value, index)
})
/*
c 3 0
b 2 1
a 1 2
*/