src/componentss/item.vue

<template>
  <p>{{ props.msg }}</p>
  <slot>default</slot>
  <slot name="title">title</slot>
  <div></div>
</template>

<script setup lang="ts">
import { onMounted } from 'vue'
const props = defineProps({
  msg: {
    type: String,
    default: 'default msg'
  }
})

const emit = defineEmits(['changeMsg'])
onMounted(() => {
  emit('changeMsg', 'todo')
})

</script>