// evolution.js
    function hideMessage() {
    $('#message').addClass('invisible');
    };

    var ready;
    ready = function() {
      $('#emergency_evolution').on('click', function(event) {
        hideMessage();
      });
    };

    $(document).ready(ready);
    $(document).on('page:load', ready);
  

    # evolution.html.erb
    <% content_for :js do %>
    <%= javascript_include_tag 'evolution', 'data-turbolinks-track' => true %>
    <script>
    hideMessage();
    </script>
    <% end %>
    ...
  

# application.html - head
    ...
    <%= yield :js if content_for?(:js) %>
    ...
  

# evolution.html.erb
      <%= f.text_area :evolution, class: "form-control" %>   ---> id="emergency_evolution
  

window.$ = function(s) {
    var c = {
    '#': 'ById',
    '.': 'sByClassName',
    '@': 'sByName',
    '=': 'sByTagName'}[s[0]];
    return document[c?'getElement'+c:'querySelectorAll'](s.slice(1))
  };

con estos 2xx bytes y sin necesidad de jQuery, puedes hacer:

$('#cabecera") o $('.cabecera)