Rails assets compile application.js file on Heroku

Question

I have couple of vendor js files and I put them in the application.html.erb of bottom of body tag as;

  <!DOCTYPE html>
    <html>
      <head>
        <meta http-equiv="content-type" content="text/html;charset=UTF-8" />
        <meta charset="utf-8" />
        <title><%= full_title(yield(:title)) %></title>
        <meta name="viewport" content="width=device-width, initial-scale=1.0, maximum-scale=1.0, user-scalable=no" />
        
        <meta name="apple-mobile-web-app-capable" content="yes">
        <meta name="apple-touch-fullscreen" content="yes">
        <meta name="apple-mobile-web-app-status-bar-style" content="default">
        <meta content="" name="description" />
        <meta content="" name="author" />
        <%= stylesheet_link_tag 'application', media: 'all', 'data-turbolinks-track' => true %>
        <meta name="viewport" content="initial-scale = 1.0,maximum-scale = 1.0" />
        
      
      <%= javascript_include_tag 'application', 'data-turbolinks-track' => true %>    
    
    
    
    
    
        <%= csrf_meta_tags %>
        
      </head>
      
      <% if (controller.controller_name == "main") %>
        <body class="fixed-header no-header">
   ...
        
      <%= javascript_include_tag 'pace/pace.min', 'data-turbolinks-track' => true %>    
      <%= javascript_include_tag 'modernizr.custom', 'data-turbolinks-track' => true %>    
      <%= javascript_include_tag 'jquery-ui/jquery-ui.min', 'data-turbolinks-track' => true %>    
      <%= javascript_include_tag 'boostrapv3/js/bootstrap.min', 'data-turbolinks-track' => true %>    
      <%= javascript_include_tag 'jquery/jquery-easy', 'data-turbolinks-track' => true %>    
      <%= javascript_include_tag 'jquery-unveil/jquery.unveil.min', 'data-turbolinks-track' => true %>    
      <%= javascript_include_tag 'jquery-bez/jquery.bez.min', 'data-turbolinks-track' => true %>    
      <%= javascript_include_tag 'jquery-ios-list/jquery.ioslist.min', 'data-turbolinks-track' => true %>    
      <%= javascript_include_tag 'jquery-actual/jquery.actual.min', 'data-turbolinks-track' => true %>    
      <%= javascript_include_tag 'jquery-scrollbar/jquery.scrollbar.min', 'data-turbolinks-track' => true %>    
      <%= javascript_include_tag 'bootstrap-select2/select2.min', 'data-turbolinks-track' => true %>    
        
...       
      </body>
    </html>

Then I declared them for Rails to be able compile (config/initializers/assets.rb)

Rails.application.config.assets.precompile += %w( pace/pace.min.js modernizr.custom.js jquery-ui/jquery-ui.min.js boostrapv3/js/bootstrap.min.js jquery/jquery-easy.js jquery-unveil/jquery.unveil.min.js jquery-bez/jquery.bez.min.js jquery-ios-list/jquery.ioslist.min.js jquery-actual/jquery.actual.min.js jquery-scrollbar/jquery.scrollbar.min.js bootstrap-select2/select2.min.js switchery/js/switchery.min.js ...)

Then I have signup to heroku and created an app then I typed;

1. bundle exec rake assets:precompile RAILS_ENV=production
2. git add .
3. git commit -m "smth"
4. git push heroku master

app works fine but the problem is in the network tab. I have application.js file but I have all the vendor js files individually. Should not be rails compiling them to 1 file ?

EDIT: I really could not figure it out how should I include vendor js files to rails app. As most of the js files work after the dom loads, I would like them to load at the end of body tag.

I removed the app and push again to heroku. I changed nothing. Now the js files works but weirdly it seems not loading.

I did not require any vendor file in application.js file.

EDIT 2

I really appreciate your answer and trying to understand one more thing.

Lets say I have a model called main.rb so I have main folder and home.html.erb file. Rails creates main.coffee ( I changed it to main.js.coffeee). So if I put all the relevant js codes into this file (main.js.coffee), whenever home.html.erb is called this js code will automatically called after page loads, is that how it works?. If so, I will organize page specific js codes like this. thank you

score 1 · Accepted Answer · edited Jun 20 '20 at 09:12

You are loading them all directly from the page as well as from the concatenated precompiled file so what you are seeing is the concatenated file being loaded and then the libraries are getting reloaded a second time from the separate js include tags in your application.html.erb file! What you need to do is require them in your app/assets/javascripts/application.js file so that they are loaded once.

For example in your app/assets/js/application.js file should be:

//= require pace/pace.min
//= require bootstrap-select2/select2.min

Do this for all the js files and then make sure if any js files aren't working properly to account for turbolinks by calling the page:change event as described here:

Rails 4: how to use $(document).ready() with turbo-links

EDIT: Loading js libraries in the Head tag is noramlly fine because they're all usually wrapped in a $(document).ready call so there is no need to force them into the end of the page like you would for php and other platforms. The Rails Way to handle this is to require them as stated in your application.js and then run bundle exec rake assets:precompile RAILS_ENV=production . Then do another git add and commit and then push to heroku!

Now, to do what you want and keep js at the bottom of specific pages you have to realize your application.html.erb gets called for every page request so you're essentially loading this script into every page like your application.js asset file is designed for. If you want to only call js on specific pages and at the bottom you can do the following:

In your application.html.erb file at the very bottom before the closing body tag you can put:

<%= yield :javascript %>

Then on all view pages where you have some script or library you'd like to include you can put at the very bottom of that view:

 <%= content_for :javascript do %>
      <script src="jquery-1.12.2.min.js"></script>
      <script type='text/javascript'>
         all your custom js here....
      </script>
<% end %>

This will yield the block of js to the :javascript in your application.html.erb at the bottom as desired.

Edit 3:

You'll notice the standard Rails application.js file has a "require_tree" directive. This basically loads all js so scripts that you have in your main.js folder will fire on anything referencing them in any other part of your application. To avoid this you can do what I do and remove these directives and call things individually. This is a bit more advanced but I'll walk you through it since it's hard to put it all together on docs scattered around the internet. This is how to load page specific assets and the ideal way to handle assets in Rails.

In your application.js file remove the require_tree and only //=require files you want application wide whether it's libraries in your vendor js folder or personal scripts. Once that is done, you'll need to change your application.html.erb file as follows:

In the head tag you can keep the "javascript_include_tag application" call since that will do what you want and pull all app. wide js files. Then at the bottom of this file above the closing body tag put:

<%= javascript_include_tag params[:controller] if ::Rails.application.assets.find_asset("#{params[:controller]}.js") %>

This will then call only the js file with the matching controller name such as 'main.js' in your example. I also then under this line use a yield to javascript code that may be on other views:

<%= yield :javascript %>

Then on pages with page specific js I put it at the very bottom of its respective view and don't add it to my assets/js folder at all:

<%= content_for :javascript do %>
  <script type='text/javascript'>
    code here
  </script>
<% end %>

Now you're almost done. Because you will be loading files by controller you need to add them to your Rails precompile list! So for example, your 'main.js' file, even if it is autocreated when generating a controller, must be added to this precompiled array with all other controller js files. To do this open up your config/initializers/assets.rb file and uncomment the following line and add all js files named after controllers:

Rails.application.config.assets.precompile += %w ( main.js )

Now restart your server and you are done! I do this for css files as well!

Note: If you have js libraries that are only used in one page you can do the //= require statement in those controller related js files. //= require is not limited to the application.js file!

Thank you for your answer. But if I require them in application.js file, then they will be called in head tag. I like them to load at the end of body tag, isnt it possible?. My application js file looks like; `//= require jquery //= require jquery_ujs //= require dropzone //= require jquery.cookie //= require toastr //= require itenary/itenaryMap //= require itenary/itenary_view //= require_tree .` So actually, I did not require all those js files here. — Shalafister's, May 20 '16 at 08:13
Yep I'll update my answer again. The Rails asset pipeline is very powerful but has also grown complex since it tries to tackle so many things. — bkunzi01, May 20 '16 at 12:46

Rails assets compile application.js file on Heroku

1 Answers1