笔记，仅供自己学习
去除顶级节点
原：
this.expendTree = res.data;
现：
this.expendTree = res.data[0].children;
去除末级节点，找到末级节点的父节点id
this.expendTree = this.dealTree(this.expendTree, "631");
// 树去掉末级节点数据
dealTree(data, id) {
var arr = [];
for (let v = 0; v < data.length; v++) {
if (data[v].type === id) {
data[v].children = null;
} else if (data[v].children) {
this.dealTree(data[v].children, "631");
}
}
arr = data;
return arr;
},