requestAnimationFrame Polyfill

RAF.js

var requestAnimationFrame = window.requestAnimationFrame || (function() { 
        var timeLast = 0;

        return window.webkitRequestAnimationFrame || window.mozRequestAnimationFrame || function(callback) {                
            var timeCurrent = (new Date()).getTime(),
                timeDelta;

            /* Dynamically set the delay on a per-tick basis to more closely match 60fps. */
            /* Technique by Erik Moller. MIT license: https://gist.github.com/paulirish/1579671. */
            timeDelta = Math.max(0, 16 - (timeCurrent - timeLast));
            timeLast = timeCurrent + timeDelta;

            return setTimeout(function() { callback(timeCurrent + timeDelta); }, timeDelta);
        };
    })();

超过16毫秒则立即执行.