两个下拉框，当选择A的时候B会跟着联动

template代码

<el-form-item label="名称：">
        <el-select v-model="formData.houseName" placeholder="请选择">
          <el-select-menu slot="menu">
            <el-select-item
              v-for="item in houseNameList"
              :label="item.houseName"
              :key="item.houseName"
              :value="item.houseName"
            ></el-select-item>
          </el-select-menu>
        </el-select>
      </el-form-item>
      <el-form-item label="号码：" prop="roomNo" class="not-inline">
        <el-select v-model="formData.roomNo"  placeholder="请选择">
          <el-select-menu slot="menu">
            <el-select-item
              v-for="item in roomNoList"
              :label="item.label"
              :value="item.value"
              :key="item.value"
            ></el-select-item>
          </el-select-menu>
        </el-select>
      </el-form-item>

script代码

watch: {
    'formData.houseName': {
      deep: true,
      handler(n, o) {
        this.roomNoList = this.houseNameList
          .filter((item) => item.houseName == n)[0]
          .roomNoList.map((item) => {
            return { label: item, value: item };
          });
      }
    }
  },