code: function addItem(item = {}) {
      if (!item.id) {
          console.warn('Cannot add menuitem. A unique identifier is required for the menuitem to work correctly.');
          return;
      }
      let el = doc.createElement('menuItem');
      // assign unique id
      item.attributes = _.assign({}, item.attributes, {
          id: item.id
      });
      // add all attributes
      setAttributes(el, item.attributes);
      // add title
      el.innerHTML = `<title>${(_.isFunction(item.name) ? item.name() : item.name)}</title>`;
      // add page reference
      el.page = item.page;
      // appends to the menu
      menuBarEl.insertBefore(el, null);
      // cache for later use
      itemsCache[item.id] = el;
  
      return el;
  }
docs: Adds menu item to the menu document.
  
  @private
  
  @param {Object} item 	The configuration realted to the menu item.