Returning HTML in the JS portion of a respond_to block throws errors in IE

Question

Here's a common pattern in my controller actions:

respond_to do |format|
  format.html {}
  format.js {
    render :layout => false
  }
end

I.e., if the request is non-AJAX, I'll send the HTML content in a layout on a brand new page. If the request is AJAX, I'll send down the same content, but without a layout (so that it can be inserted into the existing page or put into a lightbox or whatever).

So I'm always returning HTML in the format.js portion, yet Rails sets the Content-Type response header to text/javascript. This causes IE to throw this fun little error message:

alt text http://dl.dropbox.com/u/2792776/screenshots/Screen%20shot%202010-02-25%20at%205.13.49%20PM.png

Of course I could set the content-type of the response every time I did this (or use an after_filter or whatever), but it seems like I'm trying to do something relatively standard and I don't want to add additional boilerplate code.

How do I fix this problem? Alternatively, if the only way to fix the problem is to change the content-type of the response, what's the best way to achieve the behavior I want (i.e., sending down content with layout for non-AJAX and the same content without a layout for AJAX) without having to deal with these errors?

Edit: This blog post has some more info

Answer 1

Does this work for you?

respond_to do |format|
  format.html { :layout => false if request.xhr? }
  format.js {}
end

And then call the response as HTML, not JS (I have not tested it though.)

Basically, request.xhr? is the key for this solution

Answer 2

The problem is that the response is sending the Content-Type header as text/javascript which IE then tries to interpret as javascript, hence the missing ')' error message. You need the server to send response as type text/html so that the browser will not attempt to parse and execute the response content as a script but will allow you to use it as a block of HTML.

You can do this in Rails by adding something like the following to one of your controllers:

@headers["Content-Type"] = "text/html"

For example, you might add this to your Application Controller as follows:

class ApplicationController < ActionController::Base
  before_filter :fix_ct
  def fix_ct
    @headers["Content-Type"] = "text/html" 
  end    
end