构造并判断二叉搜索树-js

class Node {  constructor (val) {    this.val = val    this.left = this.right = undefined  }}class Tree {  constructor (data) {    let root = new Node(data.shift())    // 遍历所有的数据    data.forEach(item => {      this.insert(root, item)    })    return root  }  insert (node, data) {    if (node.val > data) {      if (node.left === undefined) {        node.left = new Node(data)      } else {        this.insert(node.left, data)      }    } else {      if (node.right === undefined) {        node.right = new Node(data)      } else {        this.insert(node.right, data)      }    }  }  static walk (root) {    if (!root.left && !root.right) {      return true    } else if ((root.left && root.val < root.left.val) || (root.right && root.val > root.right.val)) {      return false    } else {      return Tree.walk(root.left) && Tree.walk(root.right)    }  }}export default Treeexport {  Node}