动画主循环！！

Game-main-loop.js

// see http://paulirish.com/2011/requestanimationframe-for-smart-animating/
// shim layer with setTimeout fallback
 
(function(){
 
    // chrome shipped without the time arg in m10
    var timeundefined = false;
    if (window.webkitRequestAnimationFrame){
        webkitRequestAnimationFrame(function(time){
            timeundefined = (time == undefined);
        });
    }
 
    window.requestAnimFrame = (function(){
      return window.requestAnimationFrame ||
              (!timeundefined && window.webkitRequestAnimationFrame) ||
              window.mozRequestAnimationFrame ||
              window.oRequestAnimationFrame ||
              window.msRequestAnimationFrame ||
              function(callback, element){
                return window.setTimeout(function(){
                    callback(+new Date);
                }, 1000 / 60);
              };
    })();
 
})();

window.clearRequestTimeout = function(id) {
    window.cancelAnimationFrame ? window.cancelAnimationFrame(id) :
    window.webkitCancelAnimationFrame ? window.webkitCancelAnimationFrame(id) :
    window.webkitCancelRequestAnimationFrame ? window.webkitCancelRequestAnimationFrame(id) : /* Support for legacy API */
    window.mozCancelRequestAnimationFrame ? window.mozCancelRequestAnimationFrame(id) :
    window.oCancelRequestAnimationFrame ? window.oCancelRequestAnimationFrame(id) :
    window.msCancelRequestAnimationFrame ? window.msCancelRequestAnimationFrame(id) :
    clearTimeout(id);
};

//or in this way
    var _reqAnimFrame = window.requestAnimationFrame,
	_cancelAnimFrame = window.cancelAnimationFrame,
	_getTime = Date.now || function() {
		return new Date().getTime();
	};

	//now try to determine the requestAnimationFrame and cancelAnimationFrame functions and if none are found, we'll use a setTimeout()/clearTimeout() polyfill.
	a = ["ms", "moz", "webkit", "o"];
	i = a.length;
	while (--i > -1 && !_reqAnimFrame) {
		_reqAnimFrame = window[a[i] + "RequestAnimationFrame"];
		_cancelAnimFrame = window[a[i] + "CancelAnimationFrame"] || window[a[i] + "CancelRequestAnimationFrame"];
	}

function Animation() {
    this.animeId;
    this.startAnimation = function() {
        var self = this;
        self.lastTime = +new Date();
        self.animeId = requestAnimFrame(function( time ) {
            var delayTime = time - self.lastTime;
            // doSomething( delayTime ); // do some paint and calculate
            console.log( delayTime );
            self.startAnimation();
        });
    },
    this.stopAnimation = function() {
        clearRequestTimeout( this.animeId );
    }
}