Speed up your websites: Put JavaScripts at bottom

For websites that don't do JavaScript rendering on the client, it's best practice to put script tags at the bottom of the HTML. This way, the page can start to render before scripts have been loaded and run.

The caveat is that you also have to move all other script tags from your views to the bottom of the page. This can be done with helpers.

How to implement

  1. Add the attached javascript_helper to your app.

  2. Move your javascript_include_tags out of <head> to the end of the <body> tag, and add one extra line, like this:

    <body>
      Your content...
    
      <%= javascript_include_tag "application" ... %>
      <%= include_javascripts_at_bottom %>
    </body>
    
  3. In your ERB views change

    <%= javascript_tag do %>
       alert("Hello");
    <% end %>
    

    to

    <% javascript_at_bottom do %>
      alert("Hello");
    <% end %>
    
  4. In your Haml views change

    :javascript
      alert("Hello")
    

    to

    - at_bottom do
      :javascript
        alert("Hello")
    
Tobias Kraze almost 8 years ago
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