要求

选择省后自动显示相应城市，加载页面时将所有城市一次性加载。

实现思路

通过 watch 监视所选省，省份改变后将所有城市数组根据省id进行过滤。

示例代码

<template>
  <div>

    <!-- 省份选择 -->
    <select v-model="selectedProv">
      <option v-for="item in listProv" v-bind:value="item.id" :key="item.id">{{item.name}}</option>
    </select>

    <!-- 城市选择 -->
    <select v-model="selectedCity">
      <option v-for="item in listCity" v-bind:value="item.id" :key="item.id">{{item.name}}</option>
    </select>
  </div>
</template>

<script>
export default {
  data: function () {
    return {
      selectedProv: null,
      selectedCity: null,
      listProv: [],
      listCity: [],
      cityAll: [
        { "pid": "1", "id": "1", "name": "淄博" },
        { "pid": "1", "id": "2", "name": "青岛" },
        { "pid": "2", "id": "3", "name": "东1城" },
        { "pid": "2", "id": "4", "name": "天2上" }],
    }
  },
  created: function () {
    this.getProvList();
  },
  watch: {
    selectedProv: 'getCityList'
  },
  methods: {
    //获取省份列表
    getProvList: function () {
      this.listProv = [{ "id": "1", "name": "山东" }, { "id": "2", "name": "北京" }]
    },
    // 获取当前选择省份下的城市列表
    getCityList: function () {
      let vm = this;
      this.listCity = this.cityAll.filter(function (city) {
        return city.pid == vm.selectedProv
      })
    }
  }
}
</script>