Find parent of every leaf nodes in binary tree in node js

Js program for Find parent of every leaf nodes in binary tree. Here mentioned other language solution.

/*
    Node JS program for
    Find parent of leaf nodes in binary tree
*/
// Binary Tree node
class TreeNode
{
	constructor(data)
	{
		// Set node value
		this.data = data;
		this.left = null;
		this.right = null;
	}
}
class BinaryTree
{
	constructor()
	{
		this.root = null;
	}
	//  Find the parent of leaf nodes using recursion
	leafParent(node, parent)
	{
		if (node != null)
		{
			// Check that node is leaf node or not
			if ((node.left == null && node.right == null))
			{
				if (parent == null)
				{
					// When one node of tree
					console.log(" NULL");
				}
				else
				{
					process.stdout.write("  " + parent.data);
				}
			}
			else
			{
				// Visit left subtree
				this.leafParent(node.left, node);
				// Visit right subtree
				this.leafParent(node.right, node);
			}
		}
	}
}

function main()
{
	// Create new binary trees
	var tree = new BinaryTree();
	/*
	         34 
	        / \                           
	       /   \    
	     -4     10    
	     / \     \               
	    7   12    6
	   /   / \     
	  4   6   8   
	     / \      
	    9   1       
	-----------------
	  Constructing binary tree
	*/
	tree.root = new TreeNode(34);
	tree.root.left = new TreeNode(-4);
	tree.root.left.right = new TreeNode(12);
	tree.root.left.right.left = new TreeNode(6);
	tree.root.left.right.left.left = new TreeNode(9);
	tree.root.left.right.left.right = new TreeNode(1);
	tree.root.left.right.right = new TreeNode(8);
	tree.root.left.left = new TreeNode(7);
	tree.root.left.left.left = new TreeNode(4);
	tree.root.right = new TreeNode(10);
	tree.root.right.right = new TreeNode(6);
	// Test
	tree.leafParent(tree.root, null);
}
// Start program execution
main();

Output

  7  6  6  12  10