前言

由于element plus组件里面使用的ts来写的，在用的时候属实有点小麻烦。
最后有个小案例，实现了多选和清除选中。希望对大家有帮助
先看官网Table组件的多选代码和效果。

<template>
  <el-table
    ref="multipleTableRef"
    :data="tableData"
    style="width: 100%"
    @selection-change="handleSelectionChange"
  >
    <el-table-column type="selection" width="55" />
    <el-table-column label="Date" width="120">
      <template #default="scope">{{ scope.row.date }}</template>
    </el-table-column>
    <el-table-column property="name" label="Name" width="120" />
    <el-table-column property="address" label="Address" show-overflow-tooltip />
  </el-table>
  <div style="margin-top: 20px">
    <el-button @click="toggleSelection([tableData[1], tableData[2]])"
      >Toggle selection status of second and third rows</el-button
    >
    <el-button @click="toggleSelection()">Clear selection</el-button>
  </div>
</template>

<script lang="ts" setup>
import { ref } from 'vue'
import type { ElTable } from 'element-plus'

interface User {
  date: string
  name: string
  address: string
}

const multipleTableRef = ref<InstanceType<typeof ElTable>>()
const multipleSelection = ref<User[]>([])
const toggleSelection = (rows?: User[]) => {
  if (rows) {
    rows.forEach((row) => {
      // TODO: improvement typing when refactor table
      // eslint-disable-next-line @typescript-eslint/ban-ts-comment
      // @ts-expect-error
      multipleTableRef.value!.toggleRowSelection(row, undefined)
    })
  } else {
    multipleTableRef.value!.clearSelection()
  }
}
const handleSelectionChange = (val: User[]) => {
  multipleSelection.value = val
}

const tableData: User[] = [
  {
    date: '2016-05-03',
    name: 'Tom',
    address: 'No. 189, Grove St, Los Angeles',
  },
  {
    date: '2016-05-02',
    name: 'Tom',
    address: 'No. 189, Grove St, Los Angeles',
  },
  {
    date: '2016-05-04',
    name: 'Tom',
    address: 'No. 189, Grove St, Los Angeles',
  },
  {
    date: '2016-05-01',
    name: 'Tom',
    address: 'No. 189, Grove St, Los Angeles',
  },
  {
    date: '2016-05-08',
    name: 'Tom',
    address: 'No. 189, Grove St, Los Angeles',
  },
  {
    date: '2016-05-06',
    name: 'Tom',
    address: 'No. 189, Grove St, Los Angeles',
  },
  {
    date: '2016-05-07',
    name: 'Tom',
    address: 'No. 189, Grove St, Los Angeles',
  },
]
</script>

但是我改成js后却出现了问题

问题描述和原因

一直出现toggleRowSelection和clearSelection不是方法，真的蚌埠住了。后来查资料终于搞明白了。首先多选的情况下，ref绑定了元素，以为上述的两个方法都是从multipleTableRef里面出来的，那么就是获取的这个dom有问题了。所以可能是Vue3 获取ref注册的dom元素失败了。因为在挂载之前，dom还没创建，那就要onMounted里面获取吗?那这不是废话吗，要是能在onMounted里面实现这个功能就早实现了。

问题解决

后来发现getCurrentInstance支持访问内部组件实例。
getCurrentInstance 只能在 setup 或生命周期钩子中调用。

如需在 setup 或生命周期钩子外使用，请先在 setup 中调用 getCurrentInstance() 获取该实例然后再使用。

const MyComponent = {
  setup() {
    const internalInstance = getCurrentInstance() // 有效

    const id = useComponentId() // 有效

    const handleClick = () => {
      getCurrentInstance() // 无效
      useComponentId() // 无效

      internalInstance // 有效
    }

    onMounted(() => {
      getCurrentInstance() // 有效
    })

    return () =>
      h(
        'button',
        {
          onClick: handleClick
        },
        `uid: ${id}`
      )
  }
}

// 在组合式函数中调用也可以正常执行
function useComponentId() {
  return getCurrentInstance().uid
}

所以我通过在 const instance = getCurrentInstance(); 获取组件的实例

并且发现了ref注册的Table dom。但是这又是个代理对象，为了获取代理对象中的方法，使用toRefs ——将响应式对象转换为普通对象，其中结果对象的每个 property 都是指向原始对象相应 property 的 ref。
var ultipleTabInstance = toRefs(instance.refs.multipleTableRef)
输出ultipleTabInstance 看一看，
然后就可以找到toggleRowSelection方法了

最终可以实现了table组件的多选和清除选中了

小案例

代码

<template >
  <div id="shoplist">  
 <el-table
    ref="multipleTableRef"
    :data="data.arr"
    style="width: 100%"
    height="90%"
    stripe
    @selection-change="handleSelectionChange"
  > 
     <el-table-column type="selection" width="40" /> 
     <el-table-column property="shopname" label="店名" width="120" show-overflow-tooltip/>
    <el-table-column property="score" label="评分" sortable width="80" />
     <el-table-column property="sales" label="销量" sortable width="80" />
      <el-table-column property="type" label="类型" width="70" /> 
    
   </el-table>

  <div style="margin-top: 20px; margin-left:20px">
    <el-button @click="toggleSelection(data.arr)">全选</el-button>
    <el-button @click="toggleSelection()">清除</el-button>
  </div>
  </div>
</template>

<script>
import { onMounted, ref, watch } from 'vue' ;
import { getCurrentInstance } from 'vue'
import {ElTable} from 'element-plus'
import { reactive, toRaw, toRefs } from '@vue/reactivity';
export default {
  setup () {
   const  instance = getCurrentInstance();
    const multipleTableRef = ref(null);
    const multipleSelection  = ref([]);
    var toggleSelection =(rows)=>{
       var ultipleTabInstance = toRefs(instance.refs.multipleTableRef)
       console.log(ultipleTabInstance.toggleRowSelection);
        if(rows){
          rows.forEach(row => {
           ultipleTabInstance.toggleRowSelection.value(row, undefined)
          });
        }else{
          ultipleTabInstance.clearSelection.value()
        }
      }
    onMounted(()=>{
      // console.log(multipleTableRef);
     
    })
    var handleSelectionChange =(val)=>{
     
      multipleSelection.value = val;
      
    }
   
   
   var data = reactive({
     arr:[ {
          id:1,
          shopname:"沙县小吃",
          score:5.5,
          sales:1200,
          hh:12,
          type:"快餐"
        },
      {
          id:2,
          shopname:"法式牛排餐厅",
          score:7.5,
          sales:2400,
          hh:12,
          type:"西餐"
        },
        {
          id:3,
          shopname:"沙县大吃",
          score:6.5,
          sales:200,
          hh:12,
          type:"快餐"
        },
        {
          id:4,
          shopname:"南昌瓦罐汤",
          score:6.9,
          sales:2400,
          hh:12,
          type:"快餐"
        },
      ]    
   })
  
    return {
      data,
      multipleTableRef,
     toggleSelection,
     handleSelectionChange,
    }
  },
}
</script>

<style>
 #shoplist{
      position: fixed;
      z-index: 1001;
      width: 390px;
      height: 100%;
      min-height: 100vh;
      right: 0px;
      bottom: 0px;
      padding-top: 5px;
      background-color: #f2f2f2;
      transition: 1s;
      /* overflow: hidden; */
      border: 1px solid #333;
  }
</style>

效果