The best way to code bookmarlets (with Rails)

application_helper.rb

def javascript_content(file_name)
  Rails.application.assets[file_name].source.html_safe
end

bookmarklet.js.coffee

class Bookmarklet

  constructor: ->
    alert('test')

# Initialization
bookmarklet = new Bookmarklet

index.html.erb

<a href="javascript:<%= javascript_content('bookmarklet.js') %>">Bookmarklet</a>

Also: Live Bookmarklet!

<a href="javascript:(function(){
  if (!window.Bookmarklet) {
    var script = document.createElement('script');
        script.src = '<%= asset_url('bookmarklet.js') %>';

    document.getElementsByTagName('head')[0].appendChild(script);
  } else {
    window.Bookmarklet.toggle()
  }
})();">Bookmarklet</a>