MDN study xml http request: https://developer.mozilla.org/zh-CN/docs/Web/API/XMLHttpRequest h5 api 查询 mdn地址:https://www.w3.org/TR/html50/embedded-content-0.html#htmlmediaelement 关于h5 时间如何定义:https://www.w3.org/TR/html50/embedded-content-0.html#defineTimeline 源码解析:https://www.w3.org/TR/media-source/