Function kthSmallest

javascript/0230-kth-smallest-element-in-a-bst.js:8–12

(root, k, inOrder = [])

 * @return {number}
 */
var kthSmallest = function (root, k, inOrder = []) {
    if (!root) return inOrder;

    return dfs(root, k, inOrder);
};

const dfs = (root, k, inOrder) => {
    if (root.left) kthSmallest(root.left, k, inOrder);