D8_rplf/modules/field_group/js/field_group.js

(function ($) {

  'use strict';

  /**
   * Drupal FieldGroup object.
   */
  Drupal.FieldGroup = Drupal.FieldGroup || {};
  Drupal.FieldGroup.Effects = Drupal.FieldGroup.Effects || {};
  Drupal.FieldGroup.groupWithfocus = null;

  Drupal.FieldGroup.setGroupWithfocus = function (element) {
    element.css({display: 'block'});
    Drupal.FieldGroup.groupWithfocus = element;
  };

  /**
   * Behaviors.
   */
  Drupal.behaviors.fieldGroup = {
    attach: function (context, settings) {

      settings.field_group = settings.field_group || drupalSettings.field_group;
      if (typeof settings.field_group === 'undefined') {
        return;
      }

      // Execute all of them.
      $.each(Drupal.FieldGroup.Effects, function (func) {
        // We check for a wrapper function in Drupal.field_group as
        // alternative for dynamic string function calls.
        var type = func.toLowerCase().replace('process', '');
        if (typeof settings.field_group[type] !== 'undefined' && $.isFunction(this.execute)) {
          this.execute(context, settings, settings.field_group[type]);
        }
      });

      // Add a new ID to each fieldset.
      $('.group-wrapper fieldset').each(function () {
        // Tats bad, but we have to keep the actual id to prevent layouts to break.
        var fieldgroupID = 'field_group-' + $(this).attr('id') + ' ' + $(this).attr('id');
        $(this).attr('id', fieldgroupID);
      });

      // Set the hash in url to remember last userselection.
      $('.group-wrapper ul li').each(function () {
        var fieldGroupNavigationListIndex = $(this).index();
        $(this).children('a').click(function () {
          var fieldset = $('.group-wrapper fieldset').get(fieldGroupNavigationListIndex);
          // Grab the first id, holding the wanted hashurl.
          var hashUrl = $(fieldset).attr('id').replace(/^field_group-/, '').split(' ')[0];
          window.location.hash = hashUrl;
        });
      });
    }
  };

})(jQuery);