text: function BinaryNode(data, leftChild, rightChild) {
    this.data = data;
    this.leftChild = leftChild;
    this.rightChild = rightChild;
  }
  
  var root = new BinaryNode(0, null, null);
  var node1 = new BinaryNode(1, null, null);
  var node2 = new BinaryNode(2, null, null);
  var node3 = new BinaryNode(3, null, null);
  var node4 = new BinaryNode(4, null, null);
  var node5 = new BinaryNode(5, null, null);
  var node6 = new BinaryNode(6, null, null);
  
  root.leftChild = node1;
  root.rightChild = node2;
  
  node1.leftChild = node3;
  node1.rightChild = node4;
  
  node2.leftChild = node5;
  node2.rightChild = node6;
  