Rails 3 - AJAX, response JS - How to Handle Errors

Question

Given the following controller:

def create
      if @mymodel.save
        format.js
      else
        format.js   { render :js => @mymodel.errors }
      end
end

What's the Rails way of handling a .JS error response... Do I create .js file with a different file name just for servering Errors?

Do I add an IF ELSE in the .js file?

thanks