How can I do a synchronous request with jQuery?

Question

Why don't return that function the responseText?

function LoadBookmarksAsXml()
{
  return $.ajax(
  {
    type: 'GET',
    async: false,
    url:  'http://www.google.com/bookmarks/?output=xml&num=10000'
  }).responseText;
}

(It works if I define a success-callback-function and set async to true!) Thanks in advance!!

Edit: Don't worry about the cross-domain call; user603003 says (in a comment on a now-deleted answer) that this is in a Chrome extension where cross-domain requests are allowed.

The solution if someone wants to do the same:

return $.ajax(
{
  type: 'GET',
  async: false,
  url:  'http://www.google.com/bookmarks/?output=xml&num=10000',
});

(You will get a XMLHTTPRequest object.)

Answer 1

I'm not immediately seeing why it's not returning it, but I'd still use a success callback:

function LoadBookmarksAsXml()
{
  var result;
  $.ajax(
  {
    type: 'GET',
    async: false,
    url:  'http://www.google.com/bookmarks/?output=xml&num=10000',
    success: function(data) {
        result = data;
    }
  });
  return result;
}

Even though $.ajax returns an XMLHttpRequest object (in 1.4 or earlier) or a jqXHR object (in 1.5+), I'd still prefer using a success function and an error function for clarity. Also, different versions of jQuery give you different values for responseText on error (at least on Chrome; 1.4.4 returns an empty string, 1.5.0 returns undefined).

---

If there's any way you can avoid it, avoid it. Synchronous requests completely lock up the UI of most browsers (not just your page's UI, every page in every tab that browser is managing). Since ajax requests can take a second or two (or five, or ten), this makes for a very unpleasant user experience. Nearly all the time, you can avoid it by refactoring your function so it accepts a callback to use to supply the result:

function LoadBookmarksAsXml(callback)
{
  $.ajax(
  {
    type: 'GET',
    url:  'http://www.google.com/bookmarks/?output=xml&num=10000',
    success: function(data) {
        callback(data);
    },
    error: function() {
        callback(null);
    }
  });
}

---

Off-topic: I'll be surprised if the request works at all, though, because on the face of it (unless you work for Google), that request will fail because of the Same Origin Policy. Various ways to get around the SOP:

• JSONP
• CORS (but it requires browser support and that www.google.com allow the request from your origin)
• Using YQL as a proxy