jQuery Ajax错误描述

I Know in jQuery ajax there is tools to detect error but that I want is how to describe what is the problem? 404, no internet connection, internal server error or something else?

This is my simple program

<script type="text/javascript" charset="utf-8" src="http://jquery.local/jquery-1.7.2.min.js"></script>

<script>
    function Create_new_event ()
    {
        url = "missing.php";

        $.post(url, {
        }, function(hasil) {
            alert (hasil);
        });
    }

    $(document).ajaxError(function(event, request, settings) {
        // I believe in this area I should put my code to detect problem
    });

</script>

<button onClick="Create_new_event ();">Send</button>

Yes you can achieve that with thrownError param, do this: http://jsfiddle.net/XJ7L2/

 function Create_new_event() {
   url = "missing.php";

   $.post(url, {}, function (hasil) {
       alert(hasil);
   });
 }
 $(function () {
   $('button').click(function(){
     Create_new_event();
   });
   $(document).ajaxError(function (event, request, settings, thrownError) {
     console.log(request.status  + ' : ' + thrownError);
   });
 });

When an HTTP error occurs, thrownError receives the textual portion of the HTTP status, such as "Not Found" or "Internal Server Error."

If you look at what the request parameter contains (console.log( request );), you'll see that the response code is in request.status and textual description is in request.statusText.

So something like this:

$(document).ajaxError(function(event, request, settings) {
    console.log( 'Server returned '+request.status+': '+request.statusText );
});

Demo: http://jsfiddle.net/FSfEh/

Here is an example :

$(document).ajaxError(function(e, x, settings, exception) {
            var message;
            var statusErrorMap = {
                '400' : "Server understood the request but request content was invalid.",
                '401' : "Unauthorised access.",
                '403' : "Forbidden resouce can't be accessed",
                '500' : "Internal Server Error.",
                '503' : "Service Unavailable"
            };
            if (x.status) {
                message =statusErrorMap[x.status];
                                if(!message){
                                      message="Unknow Error 
.";
                                  }
            }else if(exception=='parsererror'){
                message="Error.
Parsing JSON Request failed.";
            }else if(exception=='timeout'){
                message="Request Time out.";
            }else if(exception=='abort'){
                message="Request was aborted by the server";
            }else {
                message="Unknow Error 
.";
            }

            alert(message);
});