fps meter

var updateAvgFps = (function (fpsElm) {
	var fpsMap = [0,0,0,0,0,0,0,0,0,0],
	    avgFps = 0,
	    lastTime = new Date().getTime(),
            drawCount = 0;

    if (! fpsElm) {
		fpsElm = document.createElement("div");
		fpsElm.style.position = "absolute";
		fpsElm.style.right = "5px";
		fpsElm.style.top = "5px";
		document.body.appendChild(fpsElm);
    }

	return function () {
	
		var now = new Date().getTime(),
			delay = Math.floor(now - lastTime);
	
	    fpsMap.push(delay);
	    avgFps += delay;
	    avgFps -= fpsMap.shift();
	    lastTime = now;
	    drawCount++;

	    if(drawCount > 5) {
			fpsElm.innerHTML = Math.round(1000 / (avgFps / 10));
			drawCount = 0;
	    }
	};
})();