Implementation of depth-first search algorithm on a binary search tree in JavaScript

javascript-dfs.js

class Node {
  // stores given value and points to nothing
  constructor (value) {
    this.value = value
    this.left = null
    this.right = null
  }
}

class Tree {
  // initially just has a root variable with null assigned
  constructor () {
    this.root = null
  }

  // helper functions

  // starting from root, traverses through a tree/subtree and
  // inserts new node depending on its value
  traverseAndInsert = (root, node) => {
    // if new node value less than root
    if (node.value < root.value) {
      // if left node null, make new node the left node
      if (root.left === null) root.left = node
      // else get traverseAndInsert to find the correct place in left subtree to insert new node
      else this.traverseAndInsert(root.left, node)
     // if new node value greater than root
    } else {
      // if right node null, make new node the right node
      if (root.right === null) root.right = node
      // else get traverseAndInsert to find the correct place in right subtree to insert new node
      else this.traverseAndInsert(root.right, node)
    }
  }

  // end of helper functions

  // to insert nodes to tree
  insert = value => {
    // create new node with given value
    let node = new Node(value)

    // if root null, make new node the root
    if (this.root === null) this.root = node
    // if not, get traverseAndInsert to find the correct place to insert new node
    else this.traverseAndInsert(this.root, node)
  }

  // -------- DFS variations ----------
  
  // left subtree -> root -> right subtree
  traverseInOrder = root => {
    if (root !== null) {
      this.traverseInOrder(root.left)
      console.log(root.value)
      this.traverseInOrder(root.right)
    }
  }

  // root -> left subtree -> right subtree
  traversePreOrder = root => {
    if (root !== null) {
      console.log(root.value)
      this.traversePreOrder(root.left)
      this.traversePreOrder(root.right)
    }
  }

  // left subtree -> right subtree -> root
  traversePostOrder = root => {
    if (root !== null) {
      this.traversePostOrder(root.left)
      this.traversePostOrder(root.right)
      console.log(root.value)
    }
  }
}

// tests

// let tree = new Tree()

// tree.insert(7)
// tree.insert(24)
// tree.insert(9)
// tree.insert(36)
// tree.insert(21)

// console.log(tree.root)

// tree.traverseInOrder(tree.root)
// console.log('-----')
// tree.traversePreOrder(tree.root)
// console.log('-----')
// tree.traversePostOrder(tree.root)