Invert a Binary Tree in Javascript

invert-binary-tree.js

// This problem was inspired by this original tweet by Max Howell:
// Google: 90% of our engineers use the software you wrote (Homebrew), but you can’t invert a binary tree on a whiteboard so fuck off.

// So, let's invert a binary tree in Javascript

// Original Tree
//      4
//    /   \
//   2     7
//  / \   / \
// 1   3 6   9

// Simple Binary Tree (depth = 3)
var tree = {
  left: {
    left: {
      value: 1
    },
    right: {
      value: 3
    },
    value: 2
  },
  right: {
    left: {
      value: 6
    },
    right: {
      value: 9
    },
    value: 7
  },
  value: 4
}

// Recursive function to return an inverted tree
function invertTree (node) {
  if (!node) return;
  
  var right = invertTree(node.right);
  var left = invertTree(node.left);
  if (left) node.left = right;
  if (right) node.right = left;
  return node;
}

// Inverted Tree
//      4
//    /   \
//   7     2
//  / \   / \
// 9   6 3   1

// Log the original tree to the console, followed by the inverted tree
console.log(JSON.parse(JSON.stringify(tree)), invertTree(tree));

If the tree is not balanced your code will fail to invert it.
Example, try to run it with this tree:
tree = { left: null, right: { left: { value: 6 }, right: { value: 9 }, value: 7 }, value: 4 }

No need to ask if (left) and if (right) in lines 42 and 43, just set the values (even if they're null or undefined). That way unbalanced trees will work as well.

var invertTree = function(root) {
    if(!root)
        return root
    var left = invertTree(root.left)
    var right = invertTree(root.right)
    root.left = left === undefined ? null : right;
    root.right = right === undefined ? null : left;
    return root
};

This code works for all types of trees

My implementantion:

function invertTree(node) {
  if(node) {
    [node.left, node.right] = [node.right, node.left];
    
    invertTree(node.left);
    invertTree(node.right);
  }

  return node;
}

This is my way :

function invertTree(node) {
  if (!node) {
    return null;
  }

  const { left, right } = node;

  node.left = invertTree(right);
  node.right = invertTree(left);

  return node;
}