遍历树结构，当节点的children为空时，递归处理children设为undefined（递归）（整理）

//如果children为空数组，则children为 undefined
getTree() {
  this.$get('/distribution/pc/org/getTree/' + 0 + '/' + 0, {}).then((res) => {
    if (res.code == 1000) {
      this.options = this.getTreeData(res.data);  //获取树结构值
      res.data =[{
               label: '一级 1',
               children: [{
                 label: '二级 1-1',
                 children: []
               }]
             }, {
               label: '一级 2',
               children: [{
                 label: '二级 2-1',
                 children: [{
                   label: '三级 2-1-1'
                 }]
               }, {
                 label: '二级 2-2',
                 children: [{
                   label: '三级 2-2-1'
                 }]
               }]
             }, {
               label: '一级 3',
               children: []
             }]
      this.getTreeData(res.data); //获取树结构值
    }
  })
},
getTreeData(data) {
  // 循环遍历json数据
  for (var i = 0; i < data.length; i++) {
    //if(data[i].level == 1){ //可根据数据返回值-添加需要参数-此条件禁止第一列选中
      //data[i].disabled = true
    //}
    if (data[i].children.length < 1) {
      // children若为空数组，则将children设为undefined
      data[i].children = undefined;
    } else {
      // children若不为空数组，则继续 递归调用 本方法
      this.getTreeData(data[i].children);
    }
  }
  return data;
},

props： 返回参数不匹配的话，修改值比如children: 'child', 
<el-cascader :options="options" v-model="rankData.areaIdAll"
            :props="{value: 'id', label: 'name', children: 'child', multiple: true, checkStrictly: true }"
            collapse-tags style="width: 400px;" @change="change2(rankData.areaIdAll)"></el-cascader>
//获取选择后的值
change2(idList) {
  console.log(idList,'236')
  if (idList.length == 0) {
    this.areaId = [];
    return false;
  }
  var newArr1 = []; // 去重后的
  var newArr2 = []; // 重复的
  var newArr3 = []; // 只出现一次的
  if (idList.length > 1) {
    for (var i = 0; i < idList.length; i++) {
      for (var j = 0; j < idList[i].length; j++) {
        var v = idList[i][j];
        // 判断是否存在数组中，不存在在往下走
        if (!newArr1.includes(v)) {
          newArr1.push(v);
        } else {
          newArr2.push(v);
        }
      }
    }
    for (var i = 0; i < newArr1.length; i++) {
      var v = newArr1[i];
      if (!newArr2.includes(v)) {
        newArr3.push(v);
      }
    }
  } else {
    for (var i = 0; i < idList.length; i++) {
      for (var j = 0; j < idList[i].length; j++) {
        var v = idList[i][j];
        // 判断是否存在数组中，不存在在往下走
        if (!newArr1.includes(v)) {
          newArr1.push(v);
        } else {
          newArr2.push(v);
        }
      }
    }
    for (var i = 0; i < newArr1.length; i++) {
      if (newArr3.indexOf(newArr1[newArr1.length - 1]) === -1) {
        newArr3.push(newArr1[newArr1.length - 1])
      }
    }
  }
  this.areaId = newArr3;
},