SOURCE

function Node(number) {
  this.left = null;
  this.right = null;
  this.element = number;
}

function Bst() {
  this.root = null;
}

Bst.prototype = {
  constructor: Bst,
  insert: function(number) {
    var node = new Node(number);
    if (this.root === null) {
      this.root = node;
    } else {
      this.insertNode(this.root, node);
    }
  },
  insertNode: function(node, newNode) {
    if (newNode.element < node.element) {
      if (node.left === null) {
        node.left = newNode;
      } else {
        this.insertNode(node.left, newNode);
      }
    } else {
      if (node.right === null) {
        node.right = newNode;
      } else {
        this.insertNode(node.right, newNode);
      }
    }
  },
  inOrderTraverse: function(fn) {
    this.inOrderTraverseNode(this.root, fn);
  },
  inOrderTraverseNode(node, fn) {
    if (node !== null) {
      this.inOrderTraverseNode(node.left, fn);
      fn(node.element);
      this.inOrderTraverseNode(node.right, fn);
    }
  }
}


// a.insert(0, 5);
// a.insert(1, 4);

// console.log(a);
// a.removeAt(2);
// console.log(a);