Number of Substrings Containing All Three Characters LeetCode solution in JavaScript

1
/**
2
 * @param {string} s
3
 * @return {number}
4
 */
5
var numberOfSubstrings = function (s) {
6
  let ans = 0;
7
  let map = {};
8
  for (let i = 0, l = 0; i < s.length; i++) {
9
    const c = s[i];
10
    map[c] = (map[c] || 0) + 1;
11

12
    while (Object.keys(map).length == 3) {
13
      ans += s.length - i;
14
      map[s[l]]--;
15
      if (map[s[l]] == 0) {
16
        delete map[s[l]];
17
      }
18
      l++;
19
    }
20
  }
21
  return ans;
22
};