Calculate the current website FPS

fps.js

(function(){
	"use strict";

	var filterStrength = 20;
	var frameTime = 0, lastLoop = new Date, thisLoop;
	var loop = function() {
		var thisFrameTime = (thisLoop=new Date) - lastLoop;
		frameTime+= (thisFrameTime - frameTime) / filterStrength;
		lastLoop = thisLoop;

		window.requestAnimationFrame(loop);
	}
	setInterval(function(){
		console.log((1000/frameTime).toFixed(1) + " fps");
	},1000);
	loop();
})();