requestAnimationFrame代替setTimeout

1.requestAnimationFrame可以代替setTimeout做动画(一般来说，requestAnimationFrame频率为每秒60帧。)

2.兼容性IE9-不支持

3.回退兼容的写法(不支持则使用setTimeout)

//示例
var i=0;
fun();
function fun() {
console.log(i);
if(i<100) {
requestAnimationFrame(fun);
}
i++;
}

//封装
(function() {
var lastTime = 0;
var vendors = ['ms', 'moz', 'webkit', 'o'];
for (var x = 0; x < vendors.length && !window.requestAnimationFrame; ++x) {
window.requestAnimationFrame = window[vendors[x] + 'RequestAnimationFrame'];
window.cancelAnimationFrame = window[vendors[x] + 'CancelAnimationFrame'] || window[vendors[x] + 'CancelRequestAnimationFrame'];
}
if (!window.requestAnimationFrame) window.requestAnimationFrame = function(callback, element) {
var currTime = new Date().getTime();
var timeToCall = Math.max(0, 16 - (currTime - lastTime));
var id = window.setTimeout(function() {
callback(currTime + timeToCall);
}, timeToCall);
lastTime = currTime + timeToCall;
return id;
};
if (!window.cancelAnimationFrame) window.cancelAnimationFrame = function(id) {
clearTimeout(id);
};
}());

http://www.cnblogs.com/Wayou/p/requestAnimationFrame.html