Convert BST to Greater Tree LeetCode solution in JavaScript

1
var convertBST = function (root) {
2
  let sum = 0;
3
  const go = (node) => {
4
    if (!node) return;
5
    go(node.right);
6
    sum += node.val;
7
    node.val = sum;
8
    go(node.left);
9
  };
10
  go(root);
11
  return root;
12
};