```
/**
* 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 || root === p || root === q) {
return root;
}
let left = lowestCommonAncestor(root.left, p, q);
let right = lowestCommonAncestor(root.right, p, q);
return (left === null) ? right : (right === null) ? left : root;
};
```