src/items.vue

<template>
  <h1>组件基础</h1>
  <item :msg @changeMsg="changeMsg">
    <p>slot</p>
  </item>
  <input type="text" v-model="msg" />
</template>

<script setup lang="ts">
import { ref } from 'vue'
import item from './componentss/item.vue';
const msg = ref('hello item');

const changeMsg = (val: string) => {
  msg.value = val
}
</script>

<style scoped>
</style>