1、首先新建conform.vue组件，其内容为：

<template>
  <div v-if="fade">
    <div class="xtx-confirm" :class="{fade}">
      <div class="wrapper" :class="{fade}">
        <div class="header">
          <h3>{{title}}</h3>
          <a @click="cancel" href="JavaScript:;" >x</a>
        </div>
        <div class="body">
          <i class="iconfont icon-warning"></i>
          <span>{{text}}</span>
        </div>
        <div class="footer">
          <span @click="cancel" class="cancel">取消</span>
          <span @click="submit" class="submit">确认</span>
        </div>
      </div>
    </div>
  </div>
</template>
<script >
import { onMounted, ref,  } from 'vue'
export default {
  name: 'conform',
  props:{
    title: {
      type: String,
      default: '温馨提示'
    },
    text: {
      type: String,
      default: ''
    },
  },
  setup(){
    const fade = ref(false)
    const open = () => {
      fade.value = true
    }
// 取消
    const cancel = () => {
      fade.value = false
    }
// 确认
    const submit = () => {
      fade.value = false
    }
    return { fade, open, cancel, submit}
  }
}
</script>
<style scoped lang="less">
.xtx-confirm {
  position: fixed;
  left: 0;
  top: 0;
  width: 100%;
  height: 100%;
  z-index: 8888;
  background: rgba(0,0,0,0);
  &.fade {
    transition: all 0.4s;
    background: rgba(0,0,0,.5);
  }
  .wrapper {
    width: 400px;
    background: #fff;
    border-radius: 4px;
    position: absolute;
    top: 50%;
    left: 50%;
    transform: translate(-50%,-60%);
    opacity: 0;
    &.fade {
      transition: all 0.4s;
      transform: translate(-50%,-50%);
      opacity: 1;
    }
    .header,.footer {
      height: 50px;
      line-height: 50px;
      padding: 0 20px;
    }
    .body {
      padding: 20px 40px;
      font-size: 16px;
      .icon-warning {
        color: red;
        margin-right: 3px;
        font-size: 16px;
      }
    }
    .footer {
      text-align: right;
      cursor: pointer;
      .cancel{
        margin-right: 20px;
        cursor: pointer;
      }
      .submit{
        cursor: pointer;
      }
    }
    .header {
      position: relative;
      h3 {
        font-weight: normal;
        font-size: 18px;
      }
      a {
        position: absolute;
        right: 15px;
        top: 15px;
        font-size: 20px;
        width: 20px;
        height: 20px;
        line-height: 20px;
        text-align: center;
        color: #999;
        &:hover {
          color: #666;
        }
      }
    }
  }
}
</style>

2、新建Item.vue组件，（注意:重点就是复用其组件中的函数字段啥的）其内容为：

<template>
  <button  @click="show_open">打开弹窗</button>
  <conform ref="conform_ref" :text="my_text"></conform>
</template>

<script >
import conform from "@/components/conform.vue";
import {nextTick, ref} from "vue";
export default {
  name:'Item',
  components:{conform},
  setup(){
    const my_text = ref('你好呀')
    // 这段代码之所以不在这使用是因为别的地方要复用这段代码
    // const conform_ref = ref(null)
    //
    // const show_open = ()=>{
    //   conform_ref.value?.open()
    //   console.log(conform_ref.value);
    // }
    // return {my_text, conform_ref, show_open}
    return {my_text, ...open()}
  }
}

// 这段代码可以导出去用于复用
export const open = ()=>{
  const conform_ref = ref(null)
  const show_open = ()=>{
    conform_ref.value?.open()
    console.log(conform_ref.value);
  }
  return {conform_ref, show_open}
}
</script>
<style scoped>
</style>

需要注意的是：不是<script setup >这种方式才可以使用export

3、在App.vue中复用代码如下：

<template>
  <div id="modals"></div>
  <button  @click="show_open">App打开弹窗</button>
<!--  <Item></Item>-->
<!--  关于Teleport 在官网这个地方有讲解
https://cn.vuejs.org/guide/built-ins/teleport.html#multiple-teleports-on-the-same-target-->
  <Teleport to="#modals">
    <!-- 需要注意的是这里的ref必须要和open中的ref名字一样   -->
    <conform ref="conform_ref"></conform>
  </Teleport>
</template>

<script >
import conform from "@/components/conform.vue";
import {open} from '@/components/Item.vue'
export default {
  name: 'App',
  components:{conform},
  setup(){
    // ...open()中能解构出来show_open
    return{...open()}
  }
}

</script>

结果显示：