LRU Cache for Node.js

This is a fork of Monsur Hossain's jscache for browsers, which is loosely based on ASP.NET's Cache, and includes many caching options such as absolute expiration, sliding expiration, cache priority, and a callback function on purge.

npm install --save cachai

First, create a new cache object. The constructor accepts an optional integer parameter which places a limit on how many items the cache holds. Example:

var Cache = require('cachai').Cache;

var cache = new Cache();

setItem adds an item to the cache. Arguments:

• key: key to refer to the object
• value: object to cache
• options: optional parameters described below

Options available are:

• expirationAbsolute: The datetime when the item should expire

• expirationSliding: An integer representing the seconds since the last cache access after which the item should expire

• priority: How important it is to leave this item in the cache. You can use the values Cache.Priority.LOW, .NORMAL, or .HIGH, or you can just use an integer. Note that placing a priority on an item does not guarantee it will remain in cache. It can still be purged if an expiration is hit, or if the cache is full.

• onPurge: A function that gets called when the item is purged from cache. The key and value of the removed item are passed as parameters to the callback function.

Example:

cache.setItem("A", "1", {
	expirationAbsolute: null,
	expirationSliding: 60,
	priority: Cache.Priority.HIGH,
	onPurge: function(k, v) { console.log('removed', k, v); }
});

getItem retrieves an item from the cache takes one parameter, the key to retrieve returns the cached item. Example:

var item = cache.getItem("A");

removeItem removes and returns an item from the cache. If the item doesn't exist it returns null. Example:

var removed = cache.removeItem("A");

size returns the number of items in the cache. Example:

var size = cache.size();

stats returns stats about the cache, like {"hits": 1, "misses": 4}. Example:

console.dir(cache.stats());

clear removes all items from the cache. Example:

cache.clear();

You can have the cache persist its values to localStorage on browsers (using browserify or webpack).

To do this, simply create the cache with a different storage backend:

var cachai = require('cachai');
var cache = new cachai.Cache(-1, new cachai.LocalStorageCacheStorage());

All values have to be JSON stringifiable.

If you want to have multiple independent caches, pass in a namespace argument, like:

var cache = new cachai.Cache(-1, new cachai.LocalStorageCacheStorage('myNameSpace'));

If -1 is used for the cache size, the cache will be limited to the size of localStorage, which is currently 5MB on Chrome/Safari.