Code snippet for AJAX I/O niceties like following redirects and passing callback URLs.

jquery.ajax_io_patch.js

(function(){
    jQuery.ajaxSetup({
        /* this ugly shit is to ensure that Rails gets its happy little CSRF tokens */
        'beforeSend': function(xhr) {
            var token = $("meta[name='csrf-token']").attr("content");
            xhr.setRequestHeader("X-CSRF-Token", token);

            // since the anchor bit of the URL isn't sent by the
            // browser, it's not available for the rails app in
            // request.referrer.  since we use the anchor bit of the
            // URL quite a lot in our app for client-side routes we
            // will send the full URL to rails with this special
            // header so we can do fancy things like send back a
            // redirect URL upon successful logins to return the user
            // to the page they left when they were prompted to login
            xhr.setRequestHeader("X-Referrer-Url", window.location.href);
        },

        complete: (jQuery.ajax.onComplete = function(xhr) {
            // allow the backend to specify a URL to visit when the
            // action is completed (like ajax login)
            var callback_url = xhr.getResponseHeader("X-Callback-Url");
            if (!!callback_url) callback_url = "&callback_url=" + encodeURIComponent(callback_url);

            // try to handle redirects transparently
            var hash_location = xhr.getResponseHeader("X-Hash-Location");
            var location      = xhr.getResponseHeader("Location");
            if ([301, 302].indexOf(xhr.status) !== -1){
                // just change the hash if the URL is just an anchor
                // fragment
                if (hash_location) return window.location.hash = hash_location + callback_url;
                if (location)             window.location.href = location;
            }
        })
    });
})();

jquery.ajax_io_patch.md

Little jQuery hook that extends AJAX IO for Rails applications. It adds the following:

On Send:

1. scrapes the page for the csrf-token meta tag to transparently send those params down with each request in the X-CSRF-Token header.

2. adds X-Referrer-Url which includes the anchor/hash portion of the URL that standard referrer misses

On Receive:

1. looks for an X-Callback-Url header in the response and, if found, will add that as a param (after the url anchor - this is oriented towards applications with client-managed routes). this is useful if you are, for example, rendering a login page that logs in via ajax and need to communicate the post-login client-side route to the client.

2. if the response is a 301 or 302, looks for an X-Hash-Location header in the response and, if found, will change the anchor/hash portion of the existing route to the new location. basically like the Location header of a standard 30x redirect only for client-managed routes.

3. if the response is a 301 or 302, looks for the Location header in the response and, if found, will follow the redirect like a non-ajax 301 or 302 would