[JS] Given the root of a binary search tree, and an integer k, return the kth smallest value (1-indexed) of all the values of the nodes in the tree.

kthSmallest.js

** https://leetcode.com/problems/kth-smallest-element-in-a-bst/
 * Definition for a binary tree node.
 * function TreeNode(val, left, right) {
 *     this.val = (val===undefined ? 0 : val)
 *     this.left = (left===undefined ? null : left)
 *     this.right = (right===undefined ? null : right)
 * }
 */
/**
 * @param {TreeNode} root
 * @param {number} k
 * @return {number}
 */
// 1<= k <=n
// root not null
const kthSmallest = function(root, k) {
    const sortedValuesGen = inOrder(root);
    let kthSmallest;
    while(k) {
        kthSmallest = sortedValuesGen.next();
        k--;
    }
  
    return kthSmallest.value;
};

function* inOrder(node) {
    if(node.left) yield * inOrder(node.left);
    yield node.val
    if(node.right) yield * inOrder(node.right);
    
//     // non-recursive inorder traversal  
//     const stack = [null];
//     while(stack.length) {
//         while(node) {
//             stack.push(node);
//             node = node.left;
//         } 
//         const cur = stack.pop();
//         if(cur) yield cur.val;
        
//         if(cur.right) node = cur.right;    
//         else node = null;   
//     }
}