jsCache

caching.js

jsCache = {

	expirationSeconds: 60,

	cache: {},
	
	cacheFunction: function (func, parameters) {
		var value;
		
		// generate the cache key using the function definition and parameters to be passed
		var key = this.getCacheKey(func, parameters);

		// check the cache for an existing value
		if(this.cache[key]) {
			// get the value
			value = this.cache[key].value;            
			
			// reset it's expiration
			this.cache[key].slidingExpiration = this.expirationSeconds;
			console.log("Extended %s", key);
		}

		if (value)
		{		
			console.log('Retrieved %s', key);
		}
		else
		{
			value = func.apply(null, parameters);			
			this.set(key, value);			
			console.log("Stored %s", key);
		}

		return value;
	},

	getCacheKey: function (func, parameters) {
		return func + "(" + JSON.stringify(parameters) + ")";
	},
	
	get: function(key) {
		return this.cache[key].value;
	},
	
	set: function(key, value) {
		this.cache[key] = {
			value: value,
			dependencies: [], 								// not implemented
			absoluteExpiration: null,						// not implemented
			slidingExpiration: this.expirationSeconds,
			priority: 'normal',								// not implemented
			onRemoveCallback: null							// not implemented
		};
	},
	
	remove: function (key) {
		delete this.cache[key];		
		console.log("Removed %s", key);
	},
	
	start: function() {
		var self = this; 
		setInterval(function(){ return self.autoExpiration(); }, 1000);
	},
	
	autoExpiration: function () {	
		var expiredKeys = [];
		
		var size = 0;
		
		// tick down and mark as expired
		for (var key in this.cache) {
			this.cache[key].slidingExpiration--;
			
			size++;
			
			//console.log(this.cache[key].slidingExpiration);

			if (this.cache[key].slidingExpiration == 0) {
				console.log('%s expired.', key);
				expiredKeys.push(key);
			}
		}
		
		// remove the expired cache entries
		for (var x = 0; x < expiredKeys.length; x++) {
			this.remove(expiredKeys[x]);
		}
		
		console.log('%d objects in cache.', size);
		
		// for debugging only
		document.body.innerHTML = "";		
		for (var key in jsCache.cache) {
			document.write('<b>' + key + '</b>: ' + jsCache.cache[key].value + "<br>");
		}
	}	
};

// set it up
jsCache.start();

// objects and functions for testing
function example() { return new Date(); }
function noparams() { return 'test 1'; }
function params(one, two) { return one + two; }
var something = {
	test3: function(var1) { return var1; }
};

// call some functions and cache the result
console.log(jsCache.cacheFunction(example));
console.log(jsCache.cacheFunction(noparams));
console.log(jsCache.cacheFunction(params, [1, 1]));
console.log(jsCache.cacheFunction(something.test3, ['this works too']));

// notice this retrieves the cached result now
console.log(jsCache.cacheFunction(example));

// manually add some items to the cache
jsCache.set('asdf', 1);
jsCache.set('qwer', { ffff: 123});

// read some values by key
console.log(jsCache.get('qwer'));

// remove some objects by key
jsCache.remove('asdf');