前言：最近在使用el-tree组件时，传给后端需要的数据是需要拼接起来的树形结构，el-tree 在选择后返回的数据并没有我想要的数据结构，需要前端手动拼接

　　　　　　　<el-input
              placeholder="输入关键字进行过滤"
              v-model="filterArea">
            </el-input>
            <el-tree
            :data="yuanData"
            show-checkbox
            node-key="id"
            ref="el-cityTree"
            highlight-current
            @check="checkCity"
            :filter-node-method="filterNode"
            :props="{label:'name',children: 'children'}">
            </el-tree>

js处理数据，（比较长）

 data() {
    return {
      filterArea:'',
      yuanData:[],
      treeData:[],// 已选树状结构
      totreeData:[], //已选所有孙子的数组对象
      totreeId:[], // 已选孙子的Id数组
    form:{
            checked:'',
            checkedCity:[],
            checkedTree:[],
            
        },
    defaultProps: {
          children: 'children',
          label: 'name'         
        }
    }
 } ,
methods:{
    getOptions(){
        api.ajax({  
                type: 'get',
                url: url,
                success: res => {
                  this.yuanData= res  
                  this.yuanData.forEach(item =>{  //el-tree-transfer组件的第一个    pid必须为0
                    item.parentId = 0 
                  })
                          
                },
                error: err => {
                  this.$message.error(err)               
                }
            })
    },

　　checkCity(check,data){
        this.handleCheckednodes(data.checkedNodes)
      },
      handleCheckednodes(checkedNodes){
       const result = checkedNodes.filter((item)=>{
          return item.children.length == 0
       })
        this.getParentData(result)
      },
      getParentData(children){
        let list= [];
            children.forEach(x => {
              let index = list.findIndex(y => y.id == x.parentId);
              if (index == -1) {
                
                list.push({
                  id: x.parentId,
                  children:[{
                    id:x.id,
                    name:x.name,
                    parentId:x.parentId,
                    children:[]
                  }]
                })
              } else {
                list[index].id = x.parentId
                list[index].children.push(x)
              }
            })
            // console.log(list,'list')
            this.getyuanDataId(list)
      },      
      // 根据市Id取到所有选中区节点的父级信息,拼成树状结构
      getyuanDataId(area){
        let cityareas = this.getCityId()      
        citys.forEach((x,idx)=>{
          x.children.forEach((y,cidx)=>{
            area.forEach((z,iidx)=>{
              if(y.id == z.id){
                y.children.push(...z.children)
              }
            })            
          })
        })
        // console.log(citys,'cityareas')
        this.delEmptyProvince(citys)
        return citys
      },
     delEmptyProvince(citys){ // 删除citys里面区为空的省对象
      let sureCitys = []
      let index = []
           citys.forEach((x,index1)=>{
            x.children.forEach((y,index2)=>{
              if(y.children.length != 0){
                index.push(index1)         
              }
            })
           })
          var array = this.remoreSameData(index)
           array.forEach((item)=>{
             sureCitys.push(citys[item])
           })
          this.form.checkedCityTree = sureCitys
          // console.log(this.form.checkedCityTree,'tree')
          this.removeEmptyCity(this.form.checkedCityTree)      
          
          return sureCitys
          
      },

// 数组去重
      remoreSameData(index){
        var array =[];
            for(var i = 0; i < index.length; i++) { // 数组去重
                if( !array.includes( index[i]) ) {
                    array.push(index[i]);
                }
            }
        return array
      },
      // 删除 this.checkedCityTree 树形结构中没有被选中的市对象,
      removeEmptyCity(neatArr){
        var newArr =[];
        neatArr.forEach((x,index1)=>{
            var arr1=  x.children.filter(function(y){
              return y.children.length != 0
            })
            newArr.push(arr1);
            x.children=newArr[index1]
           })
           this.getneatId(neatArr)  
          //  console.log(neatArr,'data000')
      },
      getneatId(arr){  
        // this.totreeData = []
        this.form.checkedCity = []
          for(var item = 0;item < arr.length;item++){ //取到数组的最后一个区子节点的对象数组 
            if(arr[item].children&&arr[item].children.length !=0){
              this.getneatId(arr[item].children)
            }else{
              this.totreeData.push(arr[item])
            }
          }
          
          this.totreeData.forEach(item =>{  // 返回所有区节点的id         
              this.form.checkedCity.push(item.id)              
           })
          this.form.checkedCity = this.remoreSameData(this.form.checkedCity)
          // console.log(this.totreeData,'data---',this.form.checkedCity)
          // return this.totreeData
      },
　　

// 取到父级省市的树形结构，区重置为空数组[]
      getCityId(){
        let parentData = this.yuanData.map(o => Object.assign({}, JSON.parse(JSON.stringify(o))));
        
        parentData.forEach((item,idx)=>{
          item.children.forEach((child,cidx)=>{
            child.children = []
            
          })

        })
        return parentData
      },
}

数据回显，设置所有选中的孙子节点的id

setTimeout(()=>{
          this.$refs['el-cityTree'].setCheckedKeys(this.totreeId)
 })

初次处理，代码比较糙