//+ Jonas Raoni Soares Silva
//@ http://jsfromhell.com/classes/timeline [v1.0]

TimeLine = function(fps, f){
	this.fps = fps, this.frames = f;
};
with({o: TimeLine, $: TimeLine.prototype}){
	o.timers = [];
	$.running = !!($.current = +(o.timer = $.time = null));
	o.run = function(){
		var o = this;
		o.timer || (o.timer = setInterval(function(){
			for(var h, d = +(new Date), t = o.timers, i = t.length; i--;){
				(!t[i].running || ((d - t[i].time) / (1e3 / t[i].fps) > t[i].current + 1 &&
				t[i].onframe(++t[i].current), t[i].current >= t[i].frames)) &&
				(h = t.splice(i, 1)[0], h.stop(1));
			}
		}, 1));
	};
	$.start = function(c){
		var o = this, t = TimeLine;
		if(o.running) return;
		o.running = true, o.current = c || 0;
		o.time = new Date, o.onstart && o.onstart();
		if(!o.onframe || o.frames <= 0 || o.fps <= 0)
			return o.stop(1);
		t.timers.push(this), t.run();
	};
	$.stop = function(){
		var o = this;
		o.running = false;
		if(!TimeLine.timers.length)
			TimeLine.timer = clearInterval(TimeLine.timer), null;
		arguments.length && o.onstop && o.onstop();
	};
}

<div id="box" style="position: absolute; top: 100px; background: #efe; width: 100px; height: 100px">25 fps</div>
<div id="box2" style="position: absolute; top: 300px; background: #ff9; width: 100px; height: 100px">12 fps</div>

<strong>TimeLine working together with the ease in quad function.</strong><br />

<script type="text/javascript">
Math.ease = function (t, b, c, d) {
	if ((t /= d / 2) < 1)
		return c / 2 * t * t + b;
	return -c / 2 * (--t * (t - 2) - 1) + b;
};

var o = new TimeLine(25, 50), d = document, b = d.getElementById("box");
o.onframe = function(){
	b.style.left = Math.ease(this.current, 0, 400, 30) + "px";
};
o.onstart = function(){
	d.body.appendChild(d.createTextNode("Started"));
};
o.onstop = function(){
	d.body.appendChild(d.createTextNode(" - Finished (" + (((new Date) - this.time)) + " msec)"))
	d.body.appendChild(d.createElement("br"));
	this.start();
};
o.start();


var o2 = new TimeLine(12, 50), b2 = d.getElementById("box2");
o2.onframe = function(){
	b2.style.left = Math.ease(this.current, 0, 400, 30) + "px";
};
o2.onstop = function(){
	this.start();
};
o2.start();
</script>