jQuery Ajax返回

I try to load a local XML File with Jquery, with this function:

function initXML()
{
  var returnVal;
  $.ajax({
    url: 'js/xml/Menue.xml',
    dataType: 'xml',
    success: function(data) {
        alert(data);
        returnVal = data;
    },
    error: loadfail
   });
  return returnVal;
 }

and test the return value with

alert(initXML());

The first alertBox has a value, but the second alertBox is empty. What is wrong?

Thanks!

You won't get any data on this alert(initXML()) because the function initXml has an asynchronous request, at the time the alert fires, the function initXML returns undefined. You will alert something for the alert(data) though.

If you want to see the value of returnVal in an alert only after the async request is done, add this to your AJAX settings:

 complete: function(jqXHR, textStatus){
alert(returnVal);    
}

Also, my two side notes:

• Use console.log() instead of alert if you are debugging. There are few things more embarassing than alerts that pop up in production code.
• Note sure which jQuery version you're coding against, but as of jQuery 1.8, success, error, and complete have been deprecated (see https://api.jquery.com/jQuery.ajax/)