binaryTreeTraversal.js

/*
A Node has the following properties:
var data; // A number or string.
Node left; // Undefined if there is no left child.
Node right; // Undefined if there is no right child.
*/

// 1.) Root node, 2.) traverse left subtree, 3.) traverse right subtree.
function preOrder(node){
  if (node === undefined){
    return [];
  }
  return [node.data].concat(preOrder(node.left)).concat(preOrder(node.right));
}

// 1.) Traverse left subtree, 2.) root node, 3.) traverse right subtree.
function inOrder(node){
  if (node === undefined){
    return [];
  }
  return inOrder(node.left).concat([node.data]).concat(inOrder(node.right));
}

// 1.) Traverse left subtree, 2.) traverse right subtree, 3.) root node.
function postOrder(node){
  if (node === undefined){
    return [];
  }
  return postOrder(node.left).concat(postOrder(node.right)).concat([node.data]);
}