Maximum Number of Occurrences of a Substring LeetCode solution in JavaScript

1
var maxFreq = function (s, maxLetters, minSize, maxSize) {
2
  let output = 0;
3

4
  let left = 0,
5
    right = 0;
6

7
  let map = {};
8

9
  let map2 = {};
10

11
  let count = 0;
12

13
  while (right < s.length) {
14
    if (map[s[right]] === undefined) {
15
      // adding letters to map to keep track of occurences (count)
16
      map[s[right]] = 1;
17
      count++;
18
    } else {
19
      if (map[s[right]] === 0) {
20
        count++;
21
      }
22
      map[s[right]]++;
23
    }
24

25
    if (right - left + 1 > minSize) {
26
      // once over minSize removing occurence of left most letter from map and adjusting count
27

28
      map[s[left]]--;
29
      if (map[s[left]] < 1) {
30
        count--;
31
      }
32
      left++;
33
    }
34

35
    if (right - left + 1 >= minSize && count <= maxLetters) {
36
      map2[s.substring(left, right + 1)] =
37
        (map2[s.substring(left, right + 1)] || 0) + 1; // if subsitrng meets constraints of size and count add to map2;
38
    }
39

40
    right++;
41
  }
42

43
  Object.entries(map2).map(([key, val]) => (output = Math.max(output, val))); // get largest value in map2
44

45
  return output;
46
};