anchor.diff:          <%= form_tag scan_username_event_path(@event), remote: false do %>
             <div class="input-group">
               <div class="input-group">
  -              <input required type="text" class="form-control typeahead" 
  +              <input required type="text" class="form-control typeahead"
                   placeholder="Ugent username" name="username" id="username">
                 <span class="input-group-btn">
                   <button class="btn btn-primary" name="button" type="submit">
  
positive.code:             }
          }
      }
  ); 
  </script>
  
negative.code: <script>
  var json = '<%= list_registrations_event_path %>';
  var registrations = new Bloodhound({
      datumTokenizer: Bloodhound.tokenizers.obj.whitespace('name', 'email'),
      queryTokenizer: Bloodhound.tokenizers.whitespace,
      prefetch: '<%= list_registrations_event_path %>'
  });
  
  registrations.initialize();
  
  $('#username').typeahead(
      {
          hint:      true,
  