npm install --save linq

module:{
  ......
  //添加
  new webpack.ProvidePlugin({
   Enumerable: "linq"
  })
}

var selectList = [
 {
  name:""，//一级名称
  CName:"", //二级名称
  value:"" //值
 },
 {name:"",CName:"",value:""},
 ......
]

data (){
 return{  
  selectModel: [],
  multipleSelectOption:[],
 }
},
methods:{
  //将源数据转成element所需格式
  transMultipleSelectOption(){
    var level1List = Enumerable.from(this.allSelectList).distinct("o=>o.name").toArray();
       
     var newArr = level1List.map(item=>{
       let children = Enumerable.from(this.allSelectList).where((o)=>{return o.name==item.name;}).toArray();

       var options = children.map(itemc=>{
         return {"name": itemc.CName, "value":itemc.value};
       });    
       return {"name": item.name, "options":options}
     });
     this.multipleSelectOption = newArr;
  },    
  //重置options(select自动补全相关)
  remoteMethod(queryString, lists) { //lists:原始数据
     var mappedList = Enumerable.from(lists).where((o)=>{return o.CName.indexOf(queryString)!=-1 
       || o.name.indexOf(queryString)!=-1;}).toArray(); //找出匹配搜索关键字的数据集
     var level1List = Enumerable.from(mappedList).distinct("o=>o.name").toArray(); //从所匹配的数据集中找出所有一级菜单集合（含去重）
    //重新拼成element所需的数据格式
     var newArr = level1List.map(item=>{
       let children = Enumerable.from(mappedList).where((o)=>{return o.name==item.name;}).toArray();

       var options = children.map(itemc=>{
         return {"name": itemc.CName, "value":itemc.value};
       });    
       return {"name": item.name, "options":options}
     });
     this.multipleSelectOption = newArr;
  },
  //点击一级菜单全选/全不选实现
  checkAll(value){ //value: 点击的一级name
     var list = Enumerable.from(this.multipleSelectOption).where((o)=>{return o.name==value;}).toArray();
     var level2ValueList = Enumerable.from(list[0].options).select("o=>o.value").toArray(); //所有该一级下二级的value集合

     var num=0;
     level2ValueList.forEach((value)=>{
       this.selectModel2.forEach((model, index)=>{
        if(model==value){
         this.selectModel2.splice(index, 1); //如有匹配，先删除
         num++;
         return true;
        }
       })
      })

      if(num < level2ValueList.length){ //需要全选
       this.selectModel2 = this.selectModel2.concat(level2ValueList); //合并数组
      }
  
   }
},
mounted: function(){
   this.transMultipleSelectOption();
},

<el-select v-model="selectModel" multiple filterable remote reserve-keyword 
  placeholder="请输入关键词" :remote-method="(queryString)=>{
    remoteMethod(queryString, allSelectList);
  }">
  <el-option-group v-for="group in multipleSelectOption"
   :key="group.name"
   :label="group.name" 
   @click.native="checkAll(group.name)">
   <el-option v-for="item in group.options"
     :key="item.value"
     :label="item.name"
     :value="item.value">
   </el-option>
  </el-option-group>
</el-select>