Kth Smallest Element in a BST

kthSmallest.js

/**
 * Definition for a binary tree node.
 * function TreeNode(val) {
 *     this.val = val;
 *     this.left = this.right = null;
 * }
 */
/**
 * @param {TreeNode} root
 * @param {number} k
 * @return {number}
 */
var kthSmallest = function(root, k) {
    var result = null;
    var count = 0;
    var isFound = false;
    
    function recur(root) {
        if (root !== null && !isFound) {
            recur(root.left);
            count++;
            if (count === k) {
                result = root.val;
                isFound = true; 
                return;
            }
            recur(root.right);
        }
    }
    recur(root);
    return result;
};