vue3 + elementPlus实现select下拉框插入确定和取消按钮。

实现思路

Select 选择器 | Element Plus

1、select方法@visible-change这个方法是下拉框出现/隐藏时触发，当显示的时候将两个按钮插入到下拉框里面，是基于原生插入DOM的这种方式；

2、通过vue3 ref获取selectDOM，在获取select的popperPaneRef.$el （select下拉框的DOM），在基于js方法创建div `document.createElement('div')` 而div里面放入两个按钮使用div.appendChild插入按钮；

3、最后将div按钮插入到 popperPaneRef.$el（select下拉框的DOM）里就可以了，在将element-button-mini的css按钮样式复制，添加到原生按钮身上；

4、这里是无法使用el-button这种组件因为不解析，只能使用原生button，为其添加ele的样式；

具体实现看代码

<template>
  <el-table :data="tableData" border style="width: 100%">
    <el-table-column align="right" label="Date" prop="date" width="280">
      <template #header>
        <div class="headers-slot">
          <p  v-if="!isShowSelect"> Date <span @click="isShowSelect = !isShowSelect"> 🔍 </span> </p>
          <div v-else>
            🔍 <el-select
                v-model="value3"
                multiple
                placeholder="Select"
                style="width: 180px"
                @visible-change="visibleChange"
                ref="filterSelect"
            >
              <el-option
                  v-for="item in options"
                  :key="item.value"
                  :label="item.label"
                  :value="item.value"
              />
            </el-select>
          </div>
        </div>
      </template>


    </el-table-column>
    <el-table-column label="Name" prop="name" width="180"/>
    <el-table-column label="Address" prop="address"/>
  </el-table>
</template>

<script setup>
import {reactive, ref} from "vue";

const value3 = ref([])
const filterSelect = ref()
let isShowSelect = ref(false)
const options = reactive([
  {
    value: 'key-1',
    label: '今天',
  },
  {
    value: 'key-2',
    label: '明天',
  },
  {
    value: 'key-3',
    label: '后天',
  },
  {
    value: 'key-4',
    label: '昨天',
  },
  {
    value: 'key-5',
    label: '前天',
  },
])

let tableData = ref([
  {
    date: '今天',
    name: 'Tom',
    address: 'No. 189, Grove St, Los Angeles',
  },
  {
    date: '明天',
    name: 'Tom',
    address: 'No. 189, Grove St, Los Angeles',
  },
  {
    date: '后天',
    name: 'Tom',
    address: 'No. 189, Grove St, Los Angeles',
  },
  {
    date: '昨天',
    name: 'Tom',
    address: 'No. 189, Grove St, Los Angeles',
  },
  {
    date: '前天',
    name: 'Tom222',
    address: 'No. 189, Grove St, Los Angeles',
  },
])

const visibleChange = (visible) => {
  console.log(visible,filterSelect)
  // 下拉框显示隐藏
  if (visible ) {
    const ref = filterSelect.value
    // 拿到下拉选项的对象
    let popper = ref.popperPaneRef
    // 在拿到它的DOM元素
    if (popper.$el) popper = popper.$el
    // 判断是否有添加按钮
    if (!Array.from(popper.children).some(v => v.className === 'select-btn-box')) {
      // 插入按钮
      let el = document.createElement('div')
      let cancelBtn = document.createElement('button')
      let confirmBtn = document.createElement('button')
      el.className = 'select-btn-box'
      cancelBtn.className = 'select-cancel-mini-btn'
      confirmBtn.className = 'select-confirm-mini-btn'
      cancelBtn.innerText = '取消'
      confirmBtn.innerText = '确定'
      el.appendChild(cancelBtn)
      el.appendChild(confirmBtn)
      // 调用确认和取消函数
      cancelBtn.onclick = () => cancelHandle()
      confirmBtn.onclick = () => confirmHandle()
      popper.appendChild(el)
    }
  }
}

const cancelHandle = () => {
  console.log('取消',value3.value)
  isShowSelect.value = false
}

const confirmHandle = () => {
  console.log('确认',value3.value)
  isShowSelect.value = false
}
</script>
<style>
.headers-slot {
  display: flex;
  align-items: center;
  justify-content: space-around;
}
/*
 这些是按钮css，复制底层ele-btn-mini的
*/
.custom-button {
  display: inline-block;
  line-height: 1;
  white-space: nowrap;
  cursor: pointer;
  background: #fff;
  color: #fff;
  -webkit-appearance: none;
  text-align: center;
  box-sizing: border-box;
  outline: 0;
  margin: 0;
  padding: 10px 15px;
  font-size: 14px;
  border-radius: 4px;
}
.select-btn-box{
  display: flex;
  border-top: 1px solid #dfe6ec;
  width: 100%;
  height: 44px;
  align-items: center;
  justify-content:flex-end ;
}
.select-cancel-mini-btn{
  display: inline-block;
  display: inline-block;
  line-height: 1;
  white-space: nowrap;
  cursor: pointer;
  background: #FFFFFF;
  border: 1px solid #DCDFE6;
  border-color: #DCDFE6;
  color: #606266;
  -webkit-appearance: none;
  text-align: center;
  -webkit-box-sizing: border-box;
  box-sizing: border-box;
  outline: none;
  margin: 0;
  -webkit-transition: 0.1s;
  transition: 0.1s;
  font-weight: 400;
  -moz-user-select: none;
  -webkit-user-select: none;
  -ms-user-select: none;
  padding: 7px 15px;
  font-size: 12px;
  border-radius: 3px;
  margin-right: 10px;
}
.select-cancel-mini-btn:hover{
  background-color:#e4f2fe ;
  color: #349cfb;
  border-color: #afd9fd;
}
.select-confirm-mini-btn:hover{
  background-color: #339bfa;
}
.select-confirm-mini-btn{
  display: inline-block;
  line-height: 1;
  white-space: nowrap;
  cursor: pointer;
  background: #fff;
  border: 1px solid #dcdfe6;
  -webkit-appearance: none;
  text-align: center;
  box-sizing: border-box;
  outline: none;
  margin: 0;
  transition: 0.1s;
  font-weight: 500;
  -moz-user-select: none;
  -webkit-user-select: none;
  -ms-user-select: none;
  padding: 12px 20px;
  font-size: 14px;
  border-radius: 4px;
  color: #fff;
  background-color: #0080f5;
  border-color: #409eff;
  padding: 7px 15px;
  font-size: 12px;
  border-radius: 3px;
  margin-right: 10px;
}
span{
  cursor: pointer;
}
</style>