1. /**
    2.  * Definition for a binary tree node.
    3.  * function TreeNode(val) {
    4.  *     this.val = val;
    5.  *     this.left = this.right = null;
    6.  * }
    7.  */
    8. /**
    9.  * @param {TreeNode} root
    10.  * @param {TreeNode} p
    11.  * @param {TreeNode} q
    12.  * @return {TreeNode}
    13.  */
    14. var lowestCommonAncestor = function(root, p, q) {
    15.     if(!root || root === p || root === q) return root
    17.     let left = lowestCommonAncestor(root.left, p, q)
    18.     let right = lowestCommonAncestor(root.right, p, q)
    20.     if(left && right) {
    21.         return root
    22.     }
    24.     return left ? left : right
    25. };