如果没有jQuery，则可以挂钩该
open方法以
readystatechange在XHR对象被
open编辑时为每个XHR对象的事件附加一个侦听器。确保在任何Ajax发生之前运行以下代码：
// save the real openvar oldOpen = XMLHttpRequest.prototype.open;function onStateChange(event) { // fires on every readystatechange ever // use `this` to determine which XHR object fired the change event}XMLHttpRequest.prototype.open = function() { // when an XHR object is opened, add a listener for its readystatechange events this.addEventListener("readystatechange", onStateChange) // run the real `open` oldOpen.apply(this, arguments);}另外，如果您只关心成功的
load事件，则可以监听该事件，而不是
readystatechange。
