npm i -D unplugin-auto-import

import { defineConfig } from 'vite'
import vue from '@vitejs/plugin-vue' 
//引入
import AutoImport from 'unplugin-auto-import/vite' 
export default defineConfig({
  plugins: [vue(),AutoImport({//注册
    imports:['vue'],
    dts:'src/auto-import.d.ts'
  })]
})

使用

<template>
  <div>
    <button @click="flag=!flag">切换</button>
  {{flag}}
  </div>
</template>

<script setup lang="ts">
//无需在引入ref
let  flag=ref<boolean>(false)
</script>

<style scoped>

</style>