anchor.diff:      set_positions();
     };
   
  -  var track_courses_sort = $('#track_courses .sortable')
  -  track_courses_sort.sortable({
  +  var track_courses_sort = '#track_courses .sortable';
  +
  +  sortable(track_courses_sort, {
       items: ".nested-fields",
       hoverClass: 'sortable-item-hover'
  -  }).bind('sortupdate', function(e, ui) {
  -      /*
  -
  -      This event is triggered when the user stopped sorting and the DOM position has changed.
  -
  -      ui.item contains the current dragged element.
  -      ui.index contains the new index of the dragged element (considering only list items)
  -      ui.oldindex contains the old index of the dragged element (considering only list items)
  -      ui.elementIndex contains the new index of the dragged element (considering all items within sortable)
  -      ui.oldElementIndex contains the old index of the dragged element (considering all items within sortable)
  -      ui.startparent contains the element that the dragged item comes from
  -      ui.endparent contains the element that the dragged item was added to (new parent)
  -
  -      */
  +  })[0].addEventListener('sortupdate', function(e) {
         updateNestedfields();
     });
     set_positions();
  
positive.code:   </div>
    <div id='track_courses' >
      <div class='links'>
        <%= link_to_add_association 'Add Course to Track', f, :track_courses, :class => "btn btn-raised" %>
      </div>
      <h4>Courses:</h4>
      <div class="course_fields sortable">
  
negative.code:     // then remove
      var template = `<%= load_track_course_form_view(nil) %>`;
      function reorder(){
        sortable(track_courses_sort);
        updateNestedfields();
      };
      searchable_input(insertedItem.clone(), "#track_courses .course_fields",
  