子组件.vue
<template>
  <div>
    <p>这个组件按需加载</p>
    <h1>这个组件显示</h1>
  </div>
</template>

<template>
    <div class="father">
            <el-button text @click="openHadndler">
                打开
            </el-button>
        <TestCom v-if="showwFlag"  title="父组件给的标题" aa="我是aa" bb="我是bb"></TestCom>
    </div>
</template>
<script setup lang="ts">
import { defineAsyncComponent, ref } from 'vue'
const TestCom = defineAsyncComponent(() => import('../../components/TestCom.vue'))
let showwFlag=ref(false)
const openHadndler = () => { 
    showwFlag.value=true
}
</script>

const 组件名1 = defineAsyncComponent(() => import('组件路径1'))
const 组件名2 = defineAsyncComponent(() => import('组件路径2'))
const 组件名3 = defineAsyncComponent(() => import('组件路径3'))

components:{
    testcom:()=>import('../components/test-com')
}

新的 defineAsyncComponent 助手方法，用于显式地定义异步组件
component 选项重命名为 loader
Loader 函数本身不再接收 resolve 和 reject 参数，且必须返回一个 Promise

import { defineAsyncComponent } from 'vue'
import ErrorComponent from './components/ErrorComponent.vue'
import LoadingComponent from './components/LoadingComponent.vue'
// 不带选项的异步组件
const asyncPage = defineAsyncComponent(() => import('./NextPage.vue'))
// 带选项的异步组件 这个带选项的平时应该是使用的较少的
const asyncPageWithOptions = defineAsyncComponent({
  loader: () => import('./NextPage.vue'),
  delay: 200,
  timeout: 3000,
  errorComponent: ErrorComponent,
  loadingComponent: LoadingComponent
})