Morris preorder traversal in typescript

Ts program for Morris preorder traversal. Here more information.

/* 
  TypeScript program for
  Morris traversal preorder
*/
// Binary Tree Node
class TreeNode
{
	public data: number;
	public left: TreeNode;
	public right: TreeNode;
	constructor(data: number)
	{
		// Set node value
		this.data = data;
		this.left = null;
		this.right = null;
	}
}
class BinaryTree
{
	public root: TreeNode;
	constructor()
	{
		// Set the initial value of root
		this.root = null;
	}
	//  Recursive function
	// Display preorder view of binary tree
	public preorder(node: TreeNode)
	{
		if (node != null)
		{
			// Print node value
			console.log("  " + node.data);
			this.preorder(node.left);
			this.preorder(node.right);
		}
	}
	// iterative preorder tree traversal
	public morrisPreorder()
	{
		if (this.root == null)
		{
			return;
		}
		var current = this.root;
		var auxiliary: TreeNode = null;
		// iterating tree nodes
		while (current != null)
		{
			if (current.left == null)
			{
				// Print node value
				console.log("  " + current.data);
				// Visit to right childs
				current = current.right;
			}
			else
			{
				auxiliary = current.left;
				// Find rightmost node which is not
				// equal to current node
				while (auxiliary.right != null && auxiliary.right != current)
				{
					// Visit to right subtree
					auxiliary = auxiliary.right;
				}
				if (auxiliary.right != current)
				{
					// Print node value
					console.log("  " + current.data);
					// Connect rightmost right node to current node
					auxiliary.right = current;
					// Visit to left childs
					current = current.left;
				}
				else
				{
					// unlink
					auxiliary.right = null;
					// Visit to right child
					current = current.right;
				}
			}
		}
		console.log("\n");
	}
	public static main(args: string[])
	{
		// Create new tree
		var tree = new BinaryTree();
		/*
		Create Binary Tree
		         4
		       /   \
		      8     10
		     / \   /  \
		    1   6 7   -3
		       /
		      9
		*/
		// Add tree node
		tree.root = new TreeNode(4);
		tree.root.left = new TreeNode(8);
		tree.root.left.left = new TreeNode(1);
		tree.root.right = new TreeNode(10);
		tree.root.right.right = new TreeNode(-3);
		tree.root.right.left = new TreeNode(7);
		tree.root.left.right = new TreeNode(6);
		tree.root.left.right.left = new TreeNode(9);
		console.log("\n Recursive Preorder");
		// Display preorder elements
		tree.preorder(tree.root);
		console.log("\n Morris Preorder");
		tree.morrisPreorder();
	}
}
BinaryTree.main([]);
/*
 file : code.ts
 tsc --target es6 code.ts
 node code.js
 */

Output

 Recursive Preorder
  4
  8
  1
  6
  9
  10
  7
  -3

 Morris Preorder
  4
  8
  1
  6
  9
  10
  7
  -3