<el-cascader
   :options="menudata"
   :props="defaultPropsa"
    v-model="val"
    clearable
    @change="menuchange"
 ></el-cascader>

data(){
   return{
      defaultPropsa: {
        //三級(jí)聯(lián)動(dòng)
        children: "children",
        label: "label",
        value: "id",
        checkStrictly: true
      },
      menudata: [], //三級(jí)聯(lián)動(dòng)data
      val: [],
      vals: [],
  }
}

 methods:{
 //三級(jí)聯(lián)動(dòng)
    async getmenudata() {
      const { data: res } = await this.$http.get("ruixing/chanPinJiaoFuAll"); //接口數(shù)據(jù)
      //  console.log(res.data);
      this.menudata = res.data;
    },
 //element組件里的 getCheckedNodes	獲取選中的節(jié)點(diǎn)	
     getCascaderObj(val, opt) {
      return val.map(function(value, index, array) {
        for (var itm of opt) {
          if (itm.id == value) {
            opt = itm.children;
            return itm;
          }
        }
        return null;
      });
    },
  //三級(jí)聯(lián)動(dòng)change事件
    menuchange() {
      this.vals = this.getCascaderObj(this.val, this.menudata); //選中節(jié)點(diǎn)數(shù)據(jù)
     console.log(this.vals) 
    },
    }

this.$refs.tree[0].getCheckedNodes();

<el-tree
  :props="defaultProps"
  :data="item.children"
  node-key="id"
  ref="tree"
  show-checkbox
  @check="(click, checked)=>{handleCheckChange(click, checked)}"
>
</el-tree>

handleCheckChange(data, checked,) {
  console.log(checked.checkedKeys);
   console.log("全選",checked.checkedNodes);
   console.log(checked.halfCheckedKeys);
   console.log("半選",checked.halfCheckedNodes);
},