兼容各个浏览器的动画循环代码

兼容各个浏览器的动画循环代码。使用html5的requestAnimationFrame API
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 function

if (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);
};
}
)
();

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