Vue3怎么使用setup语法糖拒绝写return

<template>
  <div>父组件</div>
  <Child :title="msg" />
</template>

<script setup>
import {ref} from 'Vue'
import Child from './child.vue'
const msg = ref('父的值')  //自动返回，在template直接解套使用
</script>

<template>
  <div>子组件</div>
  <div>父组件传递的值：{{title}}</div>
</template>

<script setup>
//import {defineProps} from 'vue'   不需要引入

//语法糖必须使用defineProps替代props
const  props = defineProps({
  title: {
    type: String
  }
});
//script-setup 需要通过props.xx获取父组件传递过来的props
console.log(props.title) //父的值
</script>

<template>
  <div>子组件</div>
  <button @click="toEmits">子组件向外暴露数据</button>
</template>

<script setup>
import {ref} from 'vue'
const name = ref('我是子组件')
//1、暴露内部数据
const  emits = defineEmits(['childFn']);

const  toEmits = () => {
  //2、触发父组件中暴露的childFn方法并携带数据
  emits('childFn',name)
}
</script>

<template>
  <div>父组件</div>
  <Child  @childFn='childFn' />
  <p>接收子组件传递的数据{{childData}} </p>
</template>

<script setup>
import {ref} from 'vue'
import Child from './child.vue'
    
const childData = ref(null)    
const childFn=(e)=>{
    consloe.log('子组件触发了父组件childFn，并传递了参数e')
    childData=e.value
}    
       
</script>

<script setup>
import { ref } from 'vue'

const a = 1
const b = ref(2)
//主动暴露组件属性
defineExpose({
  a,
  b
})
</script>

<template>
  <div>父组件</div>
  <Child  ref='childRef' />
  <button @click='getChildData'>通过ref获取子组件的属性 </button>
</template>

<script setup>
import {ref} from 'vue'
import Child from './child.vue'
const childRef= ref()  //注册响应数据  
const getChildData =()=>{
  //子组件接收暴露出来得值
  console.log(childRef.value.a) //1
  console.log(childRef.value.b) //2  响应式数据
}    
</script>

<template>
  <Child msg="非porps传值子组件用attrs接收" >
    <!-- 匿名插槽 -->
    <span >默认插槽</span>
    <!-- 具名插槽 -->
    <template #title>
      <h2>具名插槽</h2>
    </template>
    <!-- 作用域插槽 -->
    <template #footer="{ scope }">
      <footer>作用域插槽——姓名：{{ scope.name }}，年龄{{ scope.age }}</footer>
    </template>
  </Child>
</template>

<script setup>
// 引入子组件
import Child from './child.vue'
</script>

<template>
  <!-- 匿名插槽 -->
  <slot />
  <!-- 具名插槽 -->
  <slot name="title" />
  <!-- 作用域插槽 -->
  <slot name="footer" :scope="state" />
  <!-- $attrs 用来获取父组件中非props的传递到子组件的参数 -->
  <p>{{ attrs.msg == $attrs.msg }}</p>
  <!--true  没想到有啥作用... -->
  <p>{{ slots == $slots }}</p>
</template>

  
<script setup>
import { useSlots, useAttrs, Reactive, toRef } from 'vue'
const state = reactive({
  name: '张三',
  age: '18'
})

const slots = useSlots()
console.log(slots.default()); //获取到默认插槽的虚拟dom对象
console.log(slots.title());   //获取到具名title插槽的虚拟dom对象
// console.log(slots.footer()); //报错  不知道为啥有插槽作用域的无法获取
//useAttrs() 用来获取父组件传递的过来的属性数据的（也就是非 props 的属性值）。
const attrs = useAttrs()
</script>

<script lang='jsx'>
import { defineComponent, useSlots } from "vue";
export default defineComponent({
  setup() {
    // 获取插槽数据
    const slots = useSlots();
    // 渲染组件
    return () => (
      <div>
        {slots.default?slots.default():''}
        {slots.title?slots.title():''}
      </div>
    );
  },
});
</script>

<script setup>
import { useRouter, useRoute } from 'vue-router'
    const route = useRoute()
    const router = useRouter()
    
    function pushWithQuery(query) {
      router.push({
        name: 'search',
        query: {
          ...route.query,
        },
      })
    }
  <script/>

import router from './router'
router.beforeEach((to,from,next)=>{

})

<script setup>
import { onBeforeRouteLeave, onBeforeRouteUpdate } from 'vue-router'

    // 与 beforeRouteLeave 相同，无法访问 `this`
    onBeforeRouteLeave((to, from) => {
      const answer = window.confirm(
        'Do you really want to leave? you have unsaved changes!'
      )
      // 取消导航并停留在同一页面上
      if (!answer) return false
    })

    const userData = ref()

    // 与 beforeRouteUpdate 相同，无法访问 `this`
    onBeforeRouteUpdate(async (to, from) => {
      //仅当 id 更改时才获取用户，例如仅 query 或 hash 值已更改
      if (to.params.id !== from.params.id) {
        userData.value = await fetchUser(to.params.id)
      }
    })
 <script/>