Number of Good Pairs LeetCode solution in JavaScript

1
var numIdenticalPairs = function (nums) {
2
  let counter = 0;
3
  let map = {};
4
  for (let num of nums) {
5
    if (map[num]) {
6
      counter += map[num];
7
      map[num]++;
8
    } else {
9
      map[num] = 1;
10
    }
11
  }
12
  return counter;
13
};