Lowest Common Ancestor of a Binary Tree

/**
Definition for a binary tree node.
function TreeNode(val) {
this.val = val;
this.left = this.right = null;
}
/ /*
@param {TreeNode} root
@param {TreeNode} p
@param {TreeNode} q
@return {TreeNode}
*/
var lowestCommonAncestor = function(root, p, q) {
  if (root === null)
    return root;
  if (root === p || root === q)
    return root;
  var left = lowestCommonAncestor(root.left, p, q);
  var right = lowestCommonAncestor(root.right, p, q);
  if (left !== null && right !== null)
    return root;
  return left === null ? right : left;
};
// if only one of the Nodes is present in the given Binary Tree, then it is returned,
// you can traverse through the returned Node and check if the other one is present.

Demo