jquery's ajax not working in facebook apps

Question

I am trying to create a facebook application, all is working fine except the ajax part that I am using to populate a second box from the item selected in first select box.

Answer 1

You are not allowed to request data from other sites than the domain the script is running on. For example, if you are running the script www.example.com/script.js, then you can only ajax files under the www.exaple.com domain, not www.facebook.com.

There are a few ways to do it:

• JSONp is a way, but it requires that facebook replies with jsonp data. Not sure if it does. More info on JSONp here.
• CSSHttpRequest (or AJACSS) is another way. Seriously doubt facbook uses this method.

Answer 2

There is a limitation when using ajax that the xmlhttp request may not be cross-domain. See https://developer.mozilla.org/En/Same_origin_policy_for_JavaScript

A common workaround for this is to make the ajax request to a backend script that will actually make the cross-domain request i.e. cURL.

Answer 3

Using FBML you can use FBJS to send JSON data type to your own script:

Here is the documentation: http://wiki.developers.facebook.com/index.php/FBJS/Examples/Ajax