<template>
 <div id="app">
 <h5>vue 省市区三联动 demo</h5>
 <city-select v-model="cityInfo"></city-select>
 <h6>v-model的值是 <code>{{ cityInfo }}</code></h6>
 <h6>从v-model得知,你选择了 <i>{{ cityName }}</i></h6>
 </div>
</template>
<script>
 import CitySelect from './components/CitySelect.vue'
 export default {
 data() {
 return {
 cityInfo: '',
 }
 },
 components: {
 CitySelect
 },
 computed: {
 cityName() {
 const names = [];
 this.cityInfo.province && names.push(this.cityInfo.province.name + ' ')
 this.cityInfo.city && names.push(this.cityInfo.city.name + ' ')
 this.cityInfo.block && names.push(this.cityInfo.block.name + ' ')
 return names.join('')
 }
 }
 }
</script>
<style lang="stylus">
 h6
 padding 10px
 border 1px dotted
 h6 i
 color #f00
 border 1px dotted #ccc
</style>

<template>
 <div class="city-select">
 <select v-model="selectedProvince" name="province">
 <option v-for="(item, index) in provinces"
 v-if="item.level === 1"
 :value="item">
 {{ item.name }}
 </option>
 </select>
 <select v-model="selectedCity" name="city">
 <option
 v-for="(item, index) in cities"
 :value="item">
 {{ item.name }}
 </option>
 </select>
 <select v-model="selectedBlock" name="block">
 <option
 v-for="(item, index) in blocks"
 :value="item">
 {{ item.name }}
 </option>
 </select>
 </div>
</template>
<script>
/**
 * 省 市 区/县城 三联动选择器
*/
import provinces from './provinces.js'
import Vue from 'vue'
export default {
 name: 'app',
 created() {
 // 数据初始化,默认选中北京市,默认选中第一个;北京市数据为总数据的前18个
 let beijing = this.provinces.slice(0, 19)
 this.cities = beijing.filter(item => {
 if (item.level === 2) {
 return true
 }
 })
 this.selectedCity = this.cities[0]
 this.blocks = beijing.filter(item => {
 if (item.level === 3) {
 return true
 }
 })
 this.selectedBlock = this.blocks[0]
 },
 watch: {
 selectedProvince(newVal, oldVal) {
 // 港澳台数据只有一级,特殊处理
 if (newVal.sheng === '71' || newVal.sheng === '81' || newVal.sheng === '82') {
 this.cities = [newVal]
 this.blocks = [newVal]
 } else {
 this.cities = this.provinces.filter(item => {
  if (item.level === 2 && item.sheng && newVal.sheng === item.sheng) {
  return true
  }
 })
 }
 var _this = this
 // 此时在渲染DOM,渲染结束之后再选中第一个
 Vue.nextTick(() => {
 _this.selectedCity = _this.cities[0]
 _this.$emit('input', _this.info)
 })
 },
 selectedBlock() {
 var _this = this
 Vue.nextTick(() => {
 _this.$emit('input', _this.info)
 })
 },
 selectedCity(newVal) {
 // 选择了一个市,要选择区了 di是城市的代表,sheng
 if (newVal.sheng === '71' || newVal.sheng === '81' || newVal.sheng === '82') {
 this.blocks = [newVal]
 this.cities = [newVal]
 } else {
 this.blocks = this.provinces.filter(item => {
  if (item.level === 3 && item.sheng && item.sheng == newVal.sheng && item.di === newVal.di && item.name !== '市辖区') {
  return true
  }
 })
 }
 var _this = this
 Vue.nextTick(() => {
 _this.selectedBlock = _this.blocks[0]
 // 触发与 v-model相关的 input事件
 _this.$emit('input', _this.info)
 })
 }
 },
 computed: {
 info() {
 return {
 province: this.selectedProvince,
 city: this.selectedCity,
 block: this.selectedBlock
 }
 }
 },
 data() {
 return {
 selectedProvince: provinces[0],
 selectedCity: 0,
 selectedBlock: 0,
 cities: 0,
 provinces,
 blocks: 0
 }
 }
}
</script>
<style lang="stylus" scoped>
 .city-select select
 outline 0
</style>

Vue.nextTick(() => {
 _this.$emit('input', _this.info)
 })