vue下拉el-select二级联动

 <el-select
      v-model="departmentid"
      placeholder="请选择部门"
      @change="changeset"
    >
      <el-option
        v-for="item in departmentlist"
        :key="item.value"
        :label="item.name"
        :value="item.id"
      >
      </el-option>
    </el-select>
    <el-select v-model="personid" placeholder="请选择人员" :disabled="disabled">
      <el-option
        v-for="item in personlist"
        :key="item.value"
        :label="item.name"
        :value="item.id"
      >
      </el-option>
    </el-select>

data() {
    return {
      //部门
      departmentlist: [],
      departmentid: null,
      //人员
      personlist: [],
      personid: null,
      //禁用
      disabled: true,
    };
  },

  mounted() {
    this.getdepartmentlist();
  },

  methods: {
    getdepartmentlist() {
      //模拟部门数据
      let data = [
        {
          id: 1,
          name: "研发部",
        },
        {
          id: 2,
          name: "项目部",
        },
        {
          id: 3,
          name: "市场部",
        },
        {
          id: 4,
          name: "行政部",
        },
      ];
      //赋给部门下拉框
      this.departmentlist = data;
    },
        
    changeset() {
      //模拟人员数据
      let data = [
        {
          id: 1,             //人员id
          name: "张三",
          departmentid: 1,   //部门id
        },
        {
          id: 2,
          name: "李四",
          departmentid: 2,
        },
        {
          id: 3,
          name: "王五",
          departmentid: 1,
        },
        {
          id: 4,
          name: "赵六",
          departmentid: 3,
        },
        {
          id: 5,
          name: "小红",
          departmentid: 4,
        },
        {
          id: 6,
          name: "小明",
          departmentid: 4,
        },
        {
          id: 7,
          name: "小李",
          departmentid: 4,
        },
        {
          id: 8,
          name: "小张",
          departmentid: 4,
        },
      ];
      //如果部门id不为空
      if (!!this.departmentid) {
        //切换的时候人员清空，防止bug
        this.personlist = [];
        //禁用取消
        this.disabled = false;
        //遍历人员里面的数据
        data.forEach((e) => {
          console.log(e);
          //如果data里面部门id等于this.departmentid
          if (e.departmentid == this.departmentid) {
            //将符合的数据push进人员数组
            this.personlist.push(e);
          }
        });
        //选中部门，人员默认选中第一个
        if (this.personlist.length > 0) {
          this.personid = this.personlist[0].id;
        }
      } else {
		//选中的部门为空，则清空人员列表
        this.personlist = [];
        this.disabled = true;
      }
    },
  },