php-flarum/js/admin/src/components/HeaderSecondary.js

import Component from 'flarum/Component';
import SessionDropdown from 'flarum/components/SessionDropdown';
import ItemList from 'flarum/utils/ItemList';
import listItems from 'flarum/helpers/listItems';

/**
 * The `HeaderSecondary` component displays secondary header controls.
 */
export default class HeaderSecondary extends Component {
  view() {
    return (
      <ul className="Header-controls">
        {listItems(this.items().toArray())}
      </ul>
    );
  }

  config(isInitialized, context) {
    // Since this component is 'above' the content of the page (that is, it is a
    // part of the global UI that persists between routes), we will flag the DOM
    // to be retained across route changes.
    context.retain = true;
  }

  /**
   * Build an item list for the controls.
   *
   * @return {ItemList}
   */
  items() {
    const items = new ItemList();

    items.add('session', SessionDropdown.component());

    return items;
  }
}