一、巧用watch来达到三级联动效果

1.在component文件夹下创建文件夹chooseArea,创建对应文件
2.在views下面注册组件，然后在router下面配置路由

{
      path:'/chooseArea',
      component:() => import('../views/chooseArea/index.vue'
 },

3.从github下载所需要的省市区数据

area2.png

area3.png

这里使用的是省市区三级联动数据，带编码的pca-code-json文件

4.代码

<template>
    <div>
       <el-select clearable  placeholder="请选择省份" v-model="province">
            <el-option v-for="item in areas" :key="item.code" :value="item.name" :lable="item.name"></el-option>
       </el-select>
       <el-select clearable  :disabled="!province" style="margin:0 20px" placeholder="请选择城市" v-model="city">
            <el-option v-for="item in selectCity" :key="item.code" :value="item.name" :lable="item.name"></el-option>
       </el-select>
       <el-select clearable  :disabled="!province || !city"   placeholder="请选择区域" v-model="area">
            <el-option v-for="item in selectArea" :key="item.code" :value="item.name" :lable="item.name"></el-option>
       </el-select>
    </div>
</template>

<script lang="ts" setup>
import { computed, ref,watch } from 'vue'
import allAreas from '../lib/pca-code.json'


// 下拉框选择省份的值
let province = ref<string>('')
// 下拉选择城市的值
let city = ref<string>('')
// 下拉选择区域的值
let area = ref<string>('')
// 所有的省市区数据
let areas = ref(allAreas)

// 城市下拉框所有的值
let selectCity = ref<any[]>([])

// 区域下拉框所有的值
let selectArea = ref<any>([])


// 监听选择省份
watch(()=>province.value,val =>{
    if(val){
        let cities = areas.value.find(item => item.name === province.value)!.children
        selectCity.value = cities
    }
    city.value = ''
    area.value = ''
})
// 监听选择城市
watch(()=>city.value,val =>{
    if(val){
        let area = selectCity.value.find(item => item.name === city.value)!.children
        selectArea.value = area
    }
    area.value = ''
})

</script>

<style lang="scss" scoped>

</style>

二、完善省市区组件并给父组件分发事件

1.创建接口并导出

export interface AreaItem{
    name:string,
    code:string,
    children?:AreaItem[]
}

export interface Data{
    name:string,
    code:string
}

2.分发事件给父组件

let emits = defineEmits(['change'])

3.监听选择区域

watch(()=>area.value,val => {
    if(val){
        let provinceData:Data ={
            name:province.value,
            code: province.value && allAreas.find(item => item.name === province.value)!.code
        }
        let cityData:Data = {
            name:city.value,
            code:city.value && selectCity.value.find(item => item.name === city.value)!.code
        }
        let areaData:Data = {
            name:val,
            code:val && selectArea.value.find(item => item.name === val)!.code
        }
        // console.log(provinceData,cityData,areaData);
        emits('change',{
            province:provinceData,
            city:cityData,
            area:areaData
        })
    }
})

4.在注册的父组件中，引入事件
views/chooseArea/index.vue

<template>
    <div>
        <m-choose-area @change="changeArea"></m-choose-area>
    </div>
</template>

<script lang="ts" setup>
import mChooseArea from '../../components/chooseArea/src/index.vue';
let changeArea = (val:any) => {
    console.log(val);
}

</script>

三、完整代码

components/chooseArea/src/index.vue

<!--
 * @Author: error: git config user.name && git config user.email & please set dead value or install git
 * @Date: 2022-06-09 14:30:50
 * @LastEditors: error: git config user.name && git config user.email & please set dead value or install git
 * @LastEditTime: 2022-06-09 19:04:18
 * @FilePath: \mm-components\src\components\chooseArea\src\index.vue
 * @Description: 这是默认设置,请设置`customMade`, 打开koroFileHeader查看配置 进行设置: https://github.com/OBKoro1/koro1FileHeader/wiki/%E9%85%8D%E7%BD%AE
-->
<template>
    <div>
       <el-select clearable  placeholder="请选择省份" v-model="province">
            <el-option v-for="item in areas" :key="item.code" :value="item.name" :lable="item.name"></el-option>
       </el-select>
       <el-select clearable  :disabled="!province" style="margin:0 20px" placeholder="请选择城市" v-model="city">
            <el-option v-for="item in selectCity" :key="item.code" :value="item.name" :lable="item.name"></el-option>
       </el-select>
       <el-select clearable  :disabled="!province || !city"   placeholder="请选择区域" v-model="area">
            <el-option v-for="item in selectArea" :key="item.code" :value="item.name" :lable="item.name"></el-option>
       </el-select>
    </div>
</template>

<script lang="ts" setup>
import { computed, ref,watch } from 'vue'
import allAreas from '../lib/pca-code.json'

export interface AreaItem{
    name:string,
    code:string,
    children?:AreaItem[]
}

export interface Data{
    name:string,
    code:string
}

// 下拉框选择省份的值
let province = ref<string>('')
// 下拉选择城市的值
let city = ref<string>('')
// 下拉选择区域的值
let area = ref<string>('')
// 所有的省市区数据
let areas = ref(allAreas)

// 城市下拉框所有的值
let selectCity = ref<AreaItem[]>([])

// 区域下拉框所有的值
let selectArea = ref<AreaItem[]>([])

// 分发事件给父组件
let emits = defineEmits(['change'])

// 监听选择省份
watch(()=>province.value,val =>{
    if(val){
        let cities = areas.value.find(item => item.name === province.value)!.children
        selectCity.value = cities
    }
    city.value = ''
    area.value = ''
})
// 监听选择城市
watch(()=>city.value,val =>{
    if(val){
        let area = selectCity.value.find(item => item.name === city.value)!.children!
        selectArea.value = area
    }
    area.value = ''
})
// 监听选择区域
watch(()=>area.value,val => {
    if(val){
        let provinceData:Data ={
            name:province.value,
            code: province.value && allAreas.find(item => item.name === province.value)!.code
        }
        let cityData:Data = {
            name:city.value,
            code:city.value && selectCity.value.find(item => item.name === city.value)!.code
        }
        let areaData:Data = {
            name:val,
            code:val && selectArea.value.find(item => item.name === val)!.code
        }
        // console.log(provinceData,cityData,areaData);
        emits('change',{
            province:provinceData,
            city:cityData,
            area:areaData
        })
    }
    
})
</script>

<style lang="scss" scoped>

</style>

四、界面效果

省市区选择器.png

点击省选择器上的取消可以全部清除区域，点击市级选择器上的小叉叉可以清除市级和区级的内容，选择区级的小叉叉只能清除区级内容，重新选择时下级的内容也会全部清除，跟我们平时一些软件网页的选择器是一样的效果。