绑定一个Ajax请求发送时执行的函数。

返回值：jQuery

参数：

• callback (Function): 用于执行的函数。

示例：

AJAX请求发送时显示一条信息

("#msg").ajaxSend(function(request, settings){
   $(this).append("<li>Starting request at " + settings.url + "</li>");  
 }); 

Attach a function to be executed before an AJAX request is sent.

The XMLHttpRequest and settings used for that request are passed as arguments to the callback.

Return value: jQuery
Parameters:

• callback (Function): The function to execute.

Example:

Show a message before an AJAX request is sent.

 $("#msg").ajaxSend(function(request, settings){
     $(this).append("<li>Starting request at " + settings.url + "</li>"); 
 });