A month or so ago I found myself staring at my screen, I had done something stupid. Almost the entire application was finished, but when I tested it on another domain nothing worked. When I started exploring the Firefox javascript window and pasted some errors in Google, I found out I couldn’t do cross-domain XMLHttpRequests. I looked at Thijs, my boss / colleague / friend, and said: ‘We have a little problem.’ After some looking around we found out that Julien Lamarre had solved our problem.

In order to fit this solution into our Rails app, I wrote inject.js and some helpers. When plugin support came out I converted my solution to a plugin, and after some testing it is ready for the world. You can download it here.

Some comments are probably in place. The Inject.Request object doesn’t work exactly like the Ajax.Request object as it always evaluates the response from the server and doesn’t support the same arguments. Please take a look at the code, because it’s the best documentation right now.

The general idea behind the javascript is that it creates an invisible div element in the body element of the page and injects script tags into this div. The URL’s in the src attribute of the script tags are actually calls to Rails controllers and actions. You will have to return javascript from the actions if you want to change the state of the page, play nice and return a ‘text/javascript’ content-type when you do this.