overwrite javascript_tag to put all inline javascripts at the end of the page (for better performance)

Question

For better frontend performance, it's best practice to put your scripts at the very end of your HTML code.

I did that for a pretty big and complex page I'm working on right now and the problem I run into are many inline scripts in the views, mostly generated by Rails' built-in JavaScript helpers. These scripts depend on the libraries that used to be loaded in the head before so a lot of stuff stopped to work.

I know, it would be better to separate the JavaScript code totally from the HTML views, I'm a big fan of that, but this is not an option in this project and I'd like to avoid a discussion about this point here.

I found a pretty easy way to gather all the inline scripts and output them the end of the HTML code as well by overwriting the javascript_tag method.

But as I'm new to rails, I'd like to know if this is a good way to go or if there is a better way.

Here is how my code looks like:

def javascript_tag(content_or_options_with_block = nil, html_options = {}, &block)
  content =
    if block_given?
      html_options = content_or_options_with_block if content_or_options_with_block.is_a?(Hash)
      capture(&block)
    else
      content_or_options_with_block
    end

  javascript_code = content_tag(:script, javascript_cdata_section(content), html_options.merge(:type => Mime::JS))
  @_inline_javascript_code ||= ''
  @_inline_javascript_code << content

  return request.xhr? ? concat(javascript_code) : nil
end

Then I out the @_inline_javascript_code variable right before the closing HTML tag. That feels a little hacky to me, but works.

Any thoughts?

Answer 1

Are you having problems with the speed of your page load? If not, then I think you are optimizing prematurely at the cost of complicating your project. If you are, then I'd look at various different optimization strategies (minimization, combining scripts, etc.), before I'd look at changes that require modifying the default behavior of the framework.