树型结构转扁平化

 if(list.catalogList && list.catalogList.length > 0){
            const flatTree = (treeData) => {
              let result = [];
              treeData.forEach((item) => {
                // 先克隆一份数据作为第一层级的填充
                let res = JSON.parse(JSON.stringify(item));
                delete res.children;
                result.push(res);
                if (item.children && item.children.length > 0) {
                  // 如果当前children为数组并且长度大于0，才可进入flatTree()方法
                  result = result.concat(flatTree(item.children));
                }
              });
              return result;
            };
            this.catalogList = flatTree(list.catalogList);
          }else{
            this.catalogList = []
          }