vue webpack 编译 遇到错误TypeError: this._init is not a function

错误信息

89cfd7481a3e344ddd8da2f7de6fe105.png

index.html

main.js

import Vue from 'vue'; 
import VueRouter from 'vue-router'; 
import { configRouter } from './router-config'; 
//初始化 
Vue.use(VueRouter); 
const router = new VueRouter({}); 
configRouter(router); 
const App = Vue.extend({});//根組件 
router.start(App, '#app'); 
window.router = router; 

router-config.js

export function configRouter(router) { 
  router.map({ 
 '/':
 {
 component: require('./components/onlineIndex.vue') } 
}) 
}```
###onlineIndex.vue