Different types of Binary Tree Traversals implementation in javascript

binary-tree.js

function Node(key, left, right) {
    this.key = key;
    this.right = right;
    this.left = left;
}

function BinaryTree(root) {
    this.root = root;
}

BinaryTree.prototype.breadthFirst = {
    levelOrder: function (cursor) {
        const queue = [cursor];
        while (queue.length > 0) {
            cursor = queue.shift();
            process.stdout.write(cursor.key + " ");
            if (cursor.left) {
                queue.push(cursor.left);
            }
            if (cursor.right) {
                queue.push(cursor.right);
            }
        }

    }
}

BinaryTree.prototype.depthFirst = {
    inOrder: function (cursor) {
        if (!cursor) return;
        this.inOrder(cursor.left);
        process.stdout.write(cursor.key + " ");
        this.inOrder(cursor.right);
    },
    preOrder: function (cursor) {
        if (!cursor) return;
        process.stdout.write(cursor.key + " ");
        this.preOrder(cursor.left);
        this.preOrder(cursor.right);
    },
    postOrder: function (cursor) {
        if (!cursor) return;
        this.postOrder(cursor.left);
        this.postOrder(cursor.right);
        process.stdout.write(cursor.key + " ");
    }


}


let n4 = new Node('4');
let n2 = new Node('2', n4);
let n5 = new Node('5');
let n6 = new Node('6');
let n3 = new Node('3', n5, n6);
let n1 = new Node('1', n2, n3);

let b1 = new BinaryTree(n1);
console.log('----------Depth First-----------')
console.log('\n*In-order Traversal*')
b1.depthFirst.inOrder(b1.root);
console.log('\n\n*Pre-order Traversal*')
b1.depthFirst.preOrder(b1.root);
console.log('\n\n*Post-order Traversal*')
b1.depthFirst.postOrder(b1.root);

console.log('\n\n\n----------Breadth First----------')
console.log('\n*Level-order Traversal*')
b1.breadthFirst.levelOrder(b1.root);