A very rudimentary binary search tree in Javascript

index.js

var tree = new Tree();

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

function Tree() {
  this.head = null; 
}

Tree.prototype.add = function(value) {
  if(this.head == null) {
    this.head = new Node(value);
  } else {
    this.add_recursive(value, this.head);
  }
}

Tree.prototype.add_recursive = function(value, node) {
  if(value < node.value) {
    if(node.left == null) {
      node.left = new Node(value);
    } else {
      this.add_recursive(value, node.left)
    }
  } else if(value > node.value) {
    if(node.right == null) {
      node.right = new Node(value);
    } else {
      this.add_recursive(value, node.right)
    }
  }
}