Firefox setting to enable cross domain Ajax request

If you just don't want to waste your time on cross-domain issues during development and testing of your app you can use addon Force CORS for FF.

UPDATE: It seems that this addon no longer exists. But there is another option - this Chrome extension

Have you tried using jQuery's ajax request? As of version 1.3 jQuery supports certain types of cross domain ajax requests.

Quoting from the reference above:

Note: All remote (not on the same domain) requests should be specified as GET when 'script' or 'jsonp' is the dataType (because it loads script using a DOM script tag). Ajax options that require an XMLHttpRequest object are not available for these requests. The complete and success functions are called on completion, but do not receive an XHR object; the beforeSend and dataFilter functions are not called.

As of jQuery 1.2, you can load JSON data located on another domain if you specify a JSONP callback, which can be done like so: "myurl?callback=?". jQuery automatically replaces the ? with the correct method name to call, calling your specified callback. Or, if you set the dataType to "jsonp" a callback will be automatically added to your Ajax request.

Here is the thing, there is no way to "temporarily" disable cross-domain XMLHttpRequest, if you can disable it temporarily then it can be disabled permanently. This is a rather common problem in the modern-day of AJAX programming and is most often solved using the technique known as cross-domain scripting.

The idea here being is that if you call out to a cross-domain script it returns JavaScript (JSON) results that are then passed on to a function on your end.

Here is some sample code to illustrate how it may look from a JavaScript code perspective:

  function request_some_data() {
    var s = "http://my.document.url.com/my_data?p1=v1&p2=v2&callback=myfunc";

      try {
        try{
          document.write("<scr"+"ipt type='text/javascript' src='"+s+"'></scr"+"ipt>");
        } 
        catch(e){
          var x = document.createElement("script");
          x.src = s;
          document.getElementsByTagName("head")[0].appendChild(x);
        }
      }
      catch (e) {
        alert(e.message);
      }
   }

You will then define a function in your code that receives the data and in the server you "handle" the callback case, here is the client-side JavaScript:

function myfunc(data) {
  alert(data);
}

And on the server side, here i'm giving a PHP example but this can be done just as easily in Java or what-ever your server-side technology is:

<?php
   if($_GET["callback"]) {
     print($_GET["callback"] . "(");
   }
   /* place your JSON object code/logic here */
   if($_GET["callback"]) {
     print(");");
   }
 ?>

Note that what you are generating on the server side winds up being some JavaScript that gets executed on the client side.

I've tried using that 'UniversalBrowswerRead' thing too and it didn't work. You might be able to add an 'allow' header, but I haven't actually tried doing it yet. It's pretty new.

You can find more information here

I'm facing this from file://. I'd like to send queries to two servers from a local HTML file (a testbed).

This particular case should not be any safety concern, but only Safari allows this.

Here is the best discussion I've found of the issue.

What about using something like mod_proxy? Then it looks to your browser like the requests are going to the same server, but they're really being forwarded to another server.

You can check out my add on for firefox. It allows to cross domain in the lastest firefox version: https://addons.mozilla.org/en-US/firefox/addon/cross-domain-cors/