Display FPS using requestAnimationFrame

gistfile1.js

var lastCalledTime;
var fps;

function requestAnimFrame(t) {

  if(!lastCalledTime) {
     lastCalledTime = new Date().getTime();
     fps = 0;
  } else {
	  delta = (t - lastCalledTime)/1000;
	  lastCalledTime = t;
	  fps = parseInt(1/delta);
	  $('#someDivElement').html(fps + ' fps');
	}
	window.requestAnimationFrame(requestAnimFrame);
}

requestAnimFrame(0);