vue3.0引入子路由如何挂载

npm install vue-router@4.0.0-beta.7

import { createRouter, createWEBHistory } from 'vue-router';
import Home from './components/Home.vue';
import About from './components/About.vue';

const routes = [
  {
    path: '/',
    name: 'home',
    component: Home
  },
  {
    path: '/about',
    name: 'about',
    component: About
  },
  {
    path: '/user',
    component: () => import( './components/User.vue'),
    children: [
      {
        path: '',
        component: () => import( './components/UserProfile.vue')
      },
      {
        path: 'posts',
        component: () => import( './components/UserPosts.vue')
      }
    ]
  }
];

const router = createRouter({
  history: createWebHistory(),
  routes
});

const app = createApp(App);

app.use(router);

app.mount('#app');

<template>
  <div>
    <h2>User</h2>
    <router-view />
  </div>
</template>

<template>
  <div>
    <h3>User Profile</h3>
  </div>
</template>