Just a simple LRU cache written in javascript. It 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. It can be used to cache data locally in the user's browser, saving a server roundtrip in AJAX heavy applications.
// Create a new cache item
// The constructor accepts an optional integer
// parameter which places a limit on how many
// items the cache holds
var cache = new Cache();
// add an item to the cache
// parameters: key - the key to refer to the object
// value - the object to cache
// options - an optional parameter described below
// the last parameter accepts an object which controls various caching options:
// 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.
// callback: 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.
cache.setItem("A", "1", {expirationAbsolute: null,
expirationSliding: 60,
priority: Cache.Priority.HIGH,
callback: function(k, v) { alert('removed ' + k); }
});
// retrieve an item from the cache
// takes one parameter, the key to retreive
// returns the cached item
cache.getItem("A");
// Remove and return an item from the cache.
// If the item doesn't exist it returns null.
cache.removeItem("A");
// Removes items from the cache which pass the provided test.
// If the test function returns true, the item will be removed.
// E.g., Remove keys which start with 'RemoveMe'
cache.removeWhere(function(k, v) { return /^RemoveMe/.test(k); });
// Returns the number of items in the cache.
cache.size();
// Return stats about the cache, like {"hits": 1, "misses": 4}
cache.stats();
// clears all items from the cache
cache.clear();You can have the cache persist its values to localStorage on browsers that support it. To do this simply create the cache with a different storage backend like:
var cache = new Cache(-1, false, new Cache.LocalStorageCacheStorage());All values have to be JSON stringifiable, which means the callback option to setItem won't work.
If you want to have multiple independent caches, pass in a namespace argument, like:
var cache = new Cache(-1, false, new Cache.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.