public function addDropdown($items, $fx, $icon = 'caret square down', $menuId = null)
    {
        $menuITems = [];
        foreach ($items as $key => $item) {
            if (is_int($key)) {
                $menuITems[] = ['name' => $item, 'value' => $item];
            } else {
                $menuITems[] = ['name' => $key, 'value' => $item];
            }
        }

        $cb = $this->setHeaderDropdown($menuITems, $icon, $menuId);

        $cb->onSelectItem(function ($menu, $item) use ($fx) {
            return call_user_func($fx, $item, $menu);
        });
    }