1.组件APP

//APP.vue
<template>
  <router-view />
</template>

//main.js
import { createApp} from 'vue'
import router from './router'
import store from './store'
const app = createApp(App)
app.use(router).mount('#app')

2.第二种直接render函数

import { createApp} from 'vue'
import router from './router'
const app = createApp({
  render() {
    return <router-view />
  }
})
// const app = createApp({
//   render: () => {
//     return <router-view />
//   }
// })
app.use(router).mount('#app')

3.第三种直接h,resolveComponent函数

import { createApp, h, resolveComponent } from 'vue'
import router from './router'
const app = createApp({
  render() {
    const tag = h(resolveComponent('router-view'))
    return tag
  }
})
app.use(router).mount('#app')