官方描述：为Vite、Webpack、Rspack、Rollup和esbuild按需自动导入API，支持TypeScript。

使用该插件的好处：以vue3为例，可以帮助我们按需自动导入api，避免每个页面都频繁的手动导入。

插件地址：https://github.com/antfu/unplugin-auto-import

安装：

npm i -D unplugin-auto-import

使用：

在vite.config.ts中添加如下配置：首先引入AutoImport，然后在plugins中调用AutoImport()方法。

import { fileURLToPath, URL } from "node:url";
import { defineConfig } from "vite";
import vue from "@vitejs/plugin-vue";
import vueJsx from "@vitejs/plugin-vue-jsx";
import AutoImport from 'unplugin-auto-import/vite'; // 引入自动导入插件

export default defineConfig({
  plugins: [vue(), vueJsx(), AutoImport({ // 自动导入插件相关配置
    imports: ['vue'], // 导入vue3相关api
    dts: 'src/auto-import.d.ts' // 在src目录下生成一个指令文件存放各种全局指令
  })],
  resolve: {
    alias: {
      "@": fileURLToPath(new URL("./src", import.meta.url)),
    },
  },
  css: {
    preprocessorOptions: {
      scss: {
        additionalData: `@import "./src/assets/bem.scss";`
      }
    }
  }
});

以上配置完成之后，会在src目录下生成auto-import.d.ts文件，里面就包含了我们能用到的所有vue3相关的api。

/* eslint-disable */
/* prettier-ignore */
// @ts-nocheck
// noinspection JSUnusedGlobalSymbols
// Generated by unplugin-auto-import
export {}
declare global {
  const EffectScope: typeof import('vue')['EffectScope']
  const computed: typeof import('vue')['computed']
  const createApp: typeof import('vue')['createApp']
  const customRef: typeof import('vue')['customRef']
  const defineAsyncComponent: typeof import('vue')['defineAsyncComponent']
  const defineComponent: typeof import('vue')['defineComponent']
  const effectScope: typeof import('vue')['effectScope']
  const getCurrentInstance: typeof import('vue')['getCurrentInstance']
  const getCurrentScope: typeof import('vue')['getCurrentScope']
  const h: typeof import('vue')['h']
  const inject: typeof import('vue')['inject']
  const isProxy: typeof import('vue')['isProxy']
  const isReactive: typeof import('vue')['isReactive']
  const isReadonly: typeof import('vue')['isReadonly']
  const isRef: typeof import('vue')['isRef']
  const markRaw: typeof import('vue')['markRaw']
  const nextTick: typeof import('vue')['nextTick']
  const onActivated: typeof import('vue')['onActivated']
  const onBeforeMount: typeof import('vue')['onBeforeMount']
  const onBeforeUnmount: typeof import('vue')['onBeforeUnmount']
  const onBeforeUpdate: typeof import('vue')['onBeforeUpdate']
  const onDeactivated: typeof import('vue')['onDeactivated']
  const onErrorCaptured: typeof import('vue')['onErrorCaptured']
  const onMounted: typeof import('vue')['onMounted']
  const onRenderTracked: typeof import('vue')['onRenderTracked']
  const onRenderTriggered: typeof import('vue')['onRenderTriggered']
  const onScopeDispose: typeof import('vue')['onScopeDispose']
  const onServerPrefetch: typeof import('vue')['onServerPrefetch']
  const onUnmounted: typeof import('vue')['onUnmounted']
  const onUpdated: typeof import('vue')['onUpdated']
  const provide: typeof import('vue')['provide']
  const reactive: typeof import('vue')['reactive']
  const readonly: typeof import('vue')['readonly']
  const ref: typeof import('vue')['ref']
  const resolveComponent: typeof import('vue')['resolveComponent']
  const shallowReactive: typeof import('vue')['shallowReactive']
  const shallowReadonly: typeof import('vue')['shallowReadonly']
  const shallowRef: typeof import('vue')['shallowRef']
  const toRaw: typeof import('vue')['toRaw']
  const toRef: typeof import('vue')['toRef']
  const toRefs: typeof import('vue')['toRefs']
  const toValue: typeof import('vue')['toValue']
  const triggerRef: typeof import('vue')['triggerRef']
  const unref: typeof import('vue')['unref']
  const useAttrs: typeof import('vue')['useAttrs']
  const useCssModule: typeof import('vue')['useCssModule']
  const useCssVars: typeof import('vue')['useCssVars']
  const useSlots: typeof import('vue')['useSlots']
  const watch: typeof import('vue')['watch']
  const watchEffect: typeof import('vue')['watchEffect']
  const watchPostEffect: typeof import('vue')['watchPostEffect']
  const watchSyncEffect: typeof import('vue')['watchSyncEffect']
}
// for type re-export
declare global {
  // @ts-ignore
  export type { Component, ComponentPublicInstance, ComputedRef, InjectionKey, PropType, Ref, VNode } from 'vue'
}

然后我们可以直接在一个vue文件中使用vue3的各种api，而无需手动引入。

eg: 以下例子中直接使用 ref ，无需手动引入。

<template>
<div class="">
    <button @click="handleClick">点击{
   
   { num }}</button>
</div>
</template>

<script lang="ts" setup>
let num = ref(1);
const handleClick = () => {
    num.value += 1
}

</script>

以上就是关于该插件在vue3中的用法介绍，该插件还有其他配置项，可以去官网自行探索。