vue實現下拉框二級聯動效果的實例代碼

"list": [
      {
        "id": "1178214681118568449",
        "title": "後端開發",
        "children": [
          {
            "id": "1178214681139539969",
            "title": "Java"
          },
          {
            "id": "1178585108407984130",
            "title": "Python"
          },
          {
            "id": "1454645056483913730",
            "title": "C++"
          },
          {
            "id": "1454645056731377666",
            "title": "C#"
          }
        ]
      },
      {
        "id": "1178214681181483010",
        "title": "前端開發",
        "children": [
          {
            "id": "1178214681210843137",
            "title": "JavaScript"
          },
          {
            "id": "1178585108454121473",
            "title": "HTML/CSS"
          }
        ]
      },
      {
        "id": "1178214681231814658",
        "title": "雲計算",
        "children": [
          {
            "id": "1178214681252786178",
            "title": "Docker"
          },
          {
            "id": "1178214681294729217",
            "title": "Linux"
          }
        ]
      },
      {
        "id": "1178214681324089345",
        "title": "系統/運維",
        "children": [
          {
            "id": "1178214681353449473",
            "title": "Linux"
          },
          {
            "id": "1178214681382809602",
            "title": "Windows"
          }
        ]
      },
      {
        "id": "1178214681399586817",
        "title": "數據庫",
        "children": [
          {
            "id": "1178214681428946945",
            "title": "MySQL"
          },
          {
            "id": "1178214681454112770",
            "title": "MongoDB"
          }
        ]
      },
      {
        "id": "1178214681483472898",
        "title": "大數據",
        "children": [
          {
            "id": "1178214681504444418",
            "title": "Hadoop"
          },
          {
            "id": "1178214681529610242",
            "title": "Spark"
          }
        ]
      },
      {
        "id": "1178214681554776066",
        "title": "人工智能",
        "children": [
          {
            "id": "1178214681584136193",
            "title": "Python"
          }
        ]
      },
      {
        "id": "1178214681613496321",
        "title": "編程語言",
        "children": [
          {
            "id": "1178214681626079234",
            "title": "Java"
          }
        ]
      }
    ]

 <!-- 所屬分類 TODO -->
      <el-form-item label="課程分類">
        <!--一級分類-->
        <el-select
          v-model="courseInfo.subjectParentId"
          placeholder="一級分類" @change="subjectLevelOneChanged">
          <el-option
            v-for="subject in subjectOneList"
            :key="subject.id"
            :label="subject.title"
            :value="subject.id"/>
        </el-select>

        <!-- 二級分類 -->
        <el-select v-model="courseInfo.subjectId" placeholder="請選擇">
          <el-option
            v-for="subject in subjectTwoList"
            :key="subject.value"
            :label="subject.title"
            :value="subject.id"/>
        </el-select>
      </el-form-item>

import course from '@/api/edu/course'
import subject from '@/api/edu/subject'
export default {
  data() {
    return {
      saveBtnDisabled: false, // 保存按鈕是否禁用
      courseInfo:{
        title: '',
        subjectId: '',      //二級分類id
        subjectParentId:'', //一級分類id
        teacherId: '',      //講師id
        lessonNum: 0,       //課時
        description: '',    //課程簡介
        cover: '/static/01.jpg',          //默認封面圖片
        price: 0
      },
      teacherList:[],  //封裝所有的講師數據
      subjectOneList:[],  //一級分類
      subjectTwoList:[] ,  //二級分類
      BASE_API: process.env.BASE_API // 接口API地址
    }
  },
  created() { //頁面渲染之前執行
    //初始化所有講師
    this.getListTeacher()
    //初始化一級分類
    this.getOneSubject()
  },
  methods: {
    //點擊某個一級分類，會觸發change事件，顯示對應的二級分類
    subjectLevelOneChanged(value){
        //value就是一級分類的id值
        //先遍歷所有的分類 裡面包含一級和二級
      for (var i = 0; i <this.subjectOneList.length; i++) {
        //每個一級分類
        var oneSubject=this.subjectOneList[i]
        //判斷：所有一級分類id和點擊一級分類id是否一樣
        if(value===oneSubject.id){  //===即比較值 還要比較類型
          //從一級分類中獲取所有的二級分類
          this.subjectTwoList=oneSubject.children
          //把二級分類Id值清空
          this.courseInfo.subjectId=''
        }
      }
    },
    //查詢所有的一級分類
    getOneSubject(){
      subject.getSubjectList()
      .then(response=>{
        this.subjectOneList=response.data.list
      })
    }
  }
}
</script>