Ruby, JavaScript, Sass, iOS. Stinky Cheese & Beer Advocate. Working at CustomInk and loving it!

Unobtrusive JS In Rails 3 With Prototype

Are you bleeding on the edge of rails 3 and need to shim up some unobtrusive JavaScript to work with your link_to code that uses a destructive :method option? I did today and here is what I did to solve it. If you are unfamiliar with the problem, and what has been happening in rails 3 with UJS, check out Piotr Solnica's blog for a good run down. Or you can check out the simple code block below.

# This Ruby
link_to 'Logout', session_path, :method => :delete

# Will out put this HTML in Rails 3
# <a href="/session" data-method="delete" data-url "/session" rel="nofollow">Logoout</a>

So no more tag soup. Yea! There was much rejoicing, but I could not find any illustrated examples of what type of JavaScript to use to back this up. There are two problems at play here. First, simple link <a> tags are not forms and hence methods like post/put/delete are not going to be solved with simple query params. Second, because link tags are not forms, there is no authenticity_token hidden in the generated form, like a button_to would generate. Let's ignore the second problem for a bit and see what I came up with for using with Prototype.

var MyJsObject = {

  linkToDelete: function(event) {
    var e = event.element();
    var a = e.readAttribute('href') ? e : e.up('a');
    var form = FORM({action:a.href, method:'post'},[
    return false;


document.observe('dom:loaded', function(){
  $$('a[data-method=delete]').each(function(a){ a.observe('click', MyJsObject.linkToDelete); });

In this example I am only covering the DELETE action. This code could be abstracted to take a "method" argument and use it. As you can see, it's just a simple iteration over the links with custom "data-method" attributes and attaching a function to it. For brevity, I am using the Builder.js methods for building DOM objects. See anything odd up there? The authentication token? You got it, destructive actions like POST/DELETE/PUT will need that token. I wrote up a great article a year or so ago that still works today titled RESTful AJAX with Forgery Protection (In Rails3) that gives me that nice global var. Check it out for the last piece to this puzzle and have fun working on the edge!