npm install element-china-area-data

import {  regionData } from 'element-china-area-data'
let that;

完整代码

<template>
  <div>
      <el-form ref="dataForm" :rules="detailRules" inline :model="detail" label-position="right" label-width="140px" style="width: 100%; padding-left: 20px">
        <el-form-item label="所属省：" prop="type">
          <el-cascader v-model="detail.province" :options="optionsProvince" placeholder="请选择省份" @change="changeProvince" clearable></el-cascader>
        </el-form-item>
        <el-form-item label="所属市：" prop="type">
          <el-cascader :options="optionsCity" placeholder="请选择市" @change="changeCity" clearable></el-cascader>
        </el-form-item>
        <el-form-item label="所属区：" prop="type">
          <el-cascader :options="optionsArea" placeholder="请选择区" clearable></el-cascader>
        </el-form-item>
      </el-form>
      
</div>
</template>

<script>
import {  regionData } from 'element-china-area-data'
let that;
export default {
  name: "",
  data() {
    return {
      regionData: regionData,
      optionsProvince: [],//省
      optionsCity: [],//市
      optionsArea: [],//区
      optionsCityAll: [],//市+区
    };
  },
  created() {
    this.getoptions()
  },
  methods: {
    // 选择省份后
    changeProvince(val) {
      this.getoptionsCity(val[0])
    },
    // 选择市
    changeCity(val) {
      console.log("changeCity", val);
      this.getoptionsArea(val[0])

    },
    // 处理地区数组
    // 获取省
    getoptions() {
      this.optionsProvince = this.regionData.map(item => {
        return { value: item.value, label: item.label };
      });
    },
    // 市
    getoptionsCity(provinceCode) {
      const cityItem = this.regionData.filter(item => {
        return item.value == provinceCode;
      })
      this.optionsCityAll = cityItem[0].children;
      for (let item1 of cityItem[0].children) {
        this.optionsCity.push({
          value: item1.value, label: item1.label
        })
      }
    },
    // 区
    getoptionsArea(val) {
      const AreaItem = this.optionsCityAll.filter(item => {
        return item.value == val;
      })
      console.log(AreaItem);
      if (AreaItem[0].children.length > 0) {
        for (let item1 of AreaItem[0].children) {
          this.optionsArea.push({
            value: item1.value, label: item1.label
          })
        }
        console.log("optionsArea+++", this.optionsArea);
      }
    },
  },
};
</script>

<style lang="scss" scoped>
</style>

效果图