开发着并不知道下一刻绘制动画的最佳时机是什么时候

window.requestNextAnimationFrame = (function () {var originalWebkitRequestAnimationFrame = undefined,wrapper = undefined,callback = undefined,geckoVersion = 0,userAgent = navigator.userAgent,index = 0,self = this;// Workaround for Chrome 10 bug where Chrome// does not pass the time to the animation functionif (window.webkitRequestAnimationFrame) {// Define the wrapper
wrapper = function (time) {if (time === undefined) {time = +new Date();}self.callback(time);};// Make the switch
originalWebkitRequestAnimationFrame = window.webkitRequestAnimationFrame;window.webkitRequestAnimationFrame = function (callback, element) {self.callback = callback;// Browser calls the wrapper and wrapper calls the callback
originalWebkitRequestAnimationFrame(wrapper, element);}}// Workaround for Gecko 2.0, which has a bug in// mozRequestAnimationFrame() that restricts animations// to 30-40 fps.if (window.mozRequestAnimationFrame) {// Check the Gecko version. Gecko is used by browsers// other than Firefox. Gecko 2.0 corresponds to// Firefox 4.0.
index = userAgent.indexOf('rv:');if (userAgent.indexOf('Gecko') != -1) {geckoVersion = userAgent.substr(index + 3, 3);if (geckoVersion === '2.0') {// Forces the return statement to fall through// to the setTimeout() function.
window.mozRequestAnimationFrame = undefined;}}}return  window.requestAnimationFrame ||window.webkitRequestAnimationFrame ||window.mozRequestAnimationFrame ||window.oRequestAnimationFrame ||window.msRequestAnimationFrame ||function (callback, element) {var start,finish;window.setTimeout(function () {start = +new Date();callback(start);finish = +new Date();self.timeout = 1000 / 60 - (finish - start);}, self.timeout);};
}());window.cancelNextRequestAnimationFrame = window.cancelRequestAnimationFrame|| window.webkitCancelAnimationFrame|| window.webkitCancelRequestAnimationFrame|| window.mozCancelRequestAnimationFrame|| window.oCancelRequestAnimationFrame|| window.msCancelRequestAnimationFrame|| clearTimeout;