js流畅动画效果备忘

window.requestAnimFrame = (function(){
        return  window.requestAnimationFrame       ||
          window.webkitRequestAnimationFrame ||
          window.mozRequestAnimationFrame    ||
          window.oRequestAnimationFrame      ||
          window.msRequestAnimationFrame     ||
          function(/* function */ callback, /* DOMElement */ element){
          window.setTimeout(callback, 1000 / 60);
        };
      })();