el-select 下拉框多选实现全选的实现

<template>
 <el-select multiple collapse-tags v-model='selectedArray' @change='changeSelect' @remove-tag='removeTag' placeholder='请选择'>
  <el-option label='全选' value='全选' @click.native='selectAll'></el-option>
  <el-option v-for='(item, index) in options' :key='index' :label='item.name' :value='item.name'></el-option>
  </el-select>
</template>

export default {
 data() {
 return {
  selectedArray: [],
  options: [
  { name: '一一', label: 'one' },
  { name: '二二', label: 'tow' },
  { name: '三三', label: 'three' },
  { name: '四四', label: 'four' },
  { name: '五五', label: 'five' }
  ]
 }
 },
 methods: {
 selectAll() {
  if (this.selectedArray.length < this.options.length) {
  this.selectedArray = []
  this.options.map((item) => {
   this.selectedArray.push(item.name)
  })
  this.selectedArray.unshift('全选')
  } else {
  this.selectedArray = []
  }
 },
 changeSelect(val) {
  if (!val.includes('全选') && val.length === this.options.length) {
  this.selectedArray.unshift('全选')
  } else if (val.includes('全选') && (val.length - 1) < this.options.length) {
  this.selectedArray = this.selectedArray.filter((item) => {
   return item !== '全选'
  })
  }
 },
 removeTag(val) {
  if (val === '全选') {
  this.selectedArray = []
  }
 }
 }
}

<template>
 <el-select multiple collapse-tags v-model='selectedArray' @change='changeSelect' placeholder='请选择'>
 <el-checkbox v-model="checked" @change='selectAll'>全选</el-checkbox>
 <el-option v-for='(item, index) in options' :key='index' :label='item.name' :value='item.name'></el-option>
 </el-select>
</template>

export default {
 data() {
 return {
  checked: false,
  selectedArray: [],
  options: [
  { name: '一一', label: 'one' },
  { name: '二二', label: 'tow' },
  { name: '三三', label: 'three' },
  { name: '四四', label: 'four' },
  { name: '五五', label: 'five' }
  ]
 }
 },
 methods: {
 selectAll() {
  this.selectedArray = []
  if (this.checked) {
  this.options.map((item) => {
   this.selectedArray.push(item.name)
  })
  } else {
  this.selectedArray = []
  }
 },
 changeSelect(val) {
  if (val.length === this.options.length) {
  this.checked = true
  } else {
  this.checked = false
  }
 }
 }
}

.el-checkbox {
 text-align: right;
 width: 100%;
 padding-right: 10px;
 }