下面两个都是youtube视频的加载进度条效果的ajax插件
一、官网:http://ricostacruz.com/nprogress/官网
github:https://github.com/rstacruz/nprogress/
二、http://www.onextrapixel.com/2013/09/02/loadingbar-js-adding-a-youtube-like-loading-bar-to-your-website/
