Failproof AJAX requests in Firefox OS

Have correct values in the manifest

The app type has to be at least privileged. No, web (hosted) apps won’t work with different domains if CORS is not enabled there.

Add the systemXHR permission too, or your XMLHttpRequests to domains without CORS enabled will instafail.

Example of the syntax for these two things in the manifest:

{
  "type": "privileged",
  "permissions": {
    "systemXHR": {
      "description": "Allows loading remote content"
    }
  }
}

Add the “magic word” when creating XMLHttpRequest objects

The magic word being the mozSystem property:

request = new XMLHttpRequest({ mozSystem: true });

You should now be able to use the request in the usual way. Remember to add an error handler in case it fails!

We are using these superfailproof requests in our privileged app template to load definitions from MDN. Have a look!

For more info