raf-polyfill.js

//requestAnimationFrame polyfill | Milos Djakonovic ( @Miloshio ) | MIT | https://github.com/milosdjakonovic/requestAnimationFrame-polyfill
(function(w){
	/**
	 * 
	 * How many times should polyfill call
	 * update callback? By canon, it should
	 * be 60 times per second, so that ideal
	 * framerate 60fps could be reached.
	 *
	 * However, even native implementations
	 * of requestAnimationFrame often cannot
	 * do 60fps, but, unlike any polyfill,
	 * they can synchronise achievable fps
	 * rate with screen refresh rate.
	 *
	 * So, leave this value 1000/60 unless
	 * you target specific browser on spec
	 * ific device that is going to work 
	 * better with custom value. I think
	 * that this is the longest comment I've
	 * written on single variable so far.
	**/	
	var FRAME_RATE_INTERVAL = 1000/60,

	/**
	 * All queued callbacks in given cycle.
	**/	
	allCallbacks = [],
	
	executeAllScheduled = false,
	
	shouldCheckCancelRaf = false,
	
	/**
	 * Callbacks queued for cancellation.
	**/	
	callbacksForCancellation = [],
	
	/**
	 * Should callback be cancelled?
	 * @param cb - callback
	**/	
	isToBeCancelled = function(cb){
		for(var i=0;i<callbacksForCancellation.length;i++){
			if(callbacksForCancellation[i] === cb ){
				callbacksForCancellation.splice(i,1);
				return true;
			}
		}
	},
	
	
	
	/**
	 * 
	 * Executes all (surprise) callbacks in
	 * and removes them from callback queue.
	 *
	**/
	executeAll = function(){
		executeAllScheduled = false;
		var _allCallbacks = allCallbacks;
		allCallbacks = [];
		for(var i=0;i<_allCallbacks.length;i++){
			if(shouldCheckCancelRaf===true){
				if (isToBeCancelled(_allCallbacks[i])){
					shouldCheckCancelRaf = false;
					return;
				}
			}
			_allCallbacks[i].apply(w, [ new Date().getTime() ] );
		}
	},
	
	/**
	 *
	 * requestAnimationFrame polyfill
	 * @param callback - callback to be queued & executed | executed
	 * @return callback
	 * 
	**/	
	raf = function(callback){
		allCallbacks.push(callback);
		if(executeAllScheduled===false){
			w.setTimeout(executeAll, FRAME_RATE_INTERVAL);
			executeAllScheduled = true;
		}
		return callback;
	},

	/**
	 *
	 * Cancels raf.
	**/	
	cancelRaf = function(callback){
		callbacksForCancellation.push(callback);
		shouldCheckCancelRaf = true;
	},


	//https://gist.github.com/paulirish/1579671
	vendors = ['ms', 'moz', 'webkit', 'o'];

    for(var x = 0; x < vendors.length && !w.requestAnimationFrame; ++x) {
        w.requestAnimationFrame = w[vendors[x]+'RequestAnimationFrame'];
        w.cancelAnimationFrame = w[vendors[x]+'CancelAnimationFrame'] 
        || w[vendors[x]+'CancelRequestAnimationFrame'];
    }

	if (!w.requestAnimationFrame) w.requestAnimationFrame = raf;
 	if (!w.cancelAnimationFrame)  w.cancelAnimationFrame  = cancelRaf;	

})(window);