Distribute Coins in Binary Tree LeetCode solution in JavaScript

1
var distributeCoins = function (root) {
2
  var moves = 0;
3
  postorder(root);
4
  return moves;
5

6
  function postorder(node) {
7
    if (!node) return 0;
8

9
    const subTotal = postorder(node.left) + postorder(node.right);
10
    const result = node.val - 1 + subTotal;
11
    moves += Math.abs(result);
12

13
    return result;
14
  }
15
};