How to use the iview.Dropdown.Menu function in iview

Button, Form, Input, Message, Dropdown, Spin } from "iview";
import { Row, Col } from "iview/src/components/grid";
Vue.component("Table", Table);
Vue.component("MenuItem", Menu.Item);
Vue.component("Menu", Menu);
Vue.component("Row", Row);
Vue.component("Col", Col);
Vue.component("Icon", Icon);
Vue.component("Button", Button);
Vue.component("TimelineItem", Timeline.Item);
Vue.component("Progress", Progress);
Vue.component("Form", Form);
Vue.component("FormItem", Form.Item);
Vue.component("Input", Input);
Vue.component("Dropdown", Dropdown);
Vue.component("DropdownMenu", Dropdown.Menu);
Vue.component("DropdownItem", Dropdown.Item);
Vue.component("Cascader", Cascader);
Vue.component("Spin", Spin);
Vue.prototype.$Message = Message;
window.$Message = Message;  // eslint-disable-line

// init vuex
const router = new Router({
    routes
});
const store = new Vuex.Store(stores);
Vue.config.debug = true;

// init vue
new Vue({
    el: "#app",

updated () {
      this.$nextTick(() => {
      });
    },
    components: {
    	'Badge': Badge,
      'Tooltip': Tooltip,
      'Icon': Icon,
      'Modal': Modal,
      'IButton': Button,
      'IMenu': Menu,
      'Submenu': Menu.Sub,
      'IMenuItem': Menu.Item,
      'MenuGroup': Menu.Group,
      'Dropdown': Dropdown,
      'DropdownMenu': Dropdown.Menu,
      'DropdownItem': Dropdown.Item,
      'Avatar': Avatar,
      'SideMenu': SideMenu
    },
    mounted() {
    	//console.log(this.$route);
    }
  };