Codility: MaxCounters Solution

1function solution(X, A) {
2  let res = Array(X).fill(0)
3  let max = 0
4  let latestMax = 0
5  for (const a of A) {
6    if (1 <= a && a <= X) {
7      if (res[a - 1] < latestMax) {
8        res[a - 1] = latestMax
9      }
10      res[a - 1] += 1
11      if (res[a - 1] > max) {
12        max = res[a - 1]
13      }
14    } else {
15      latestMax = max
16    }
17  }
18  for (const [i, r] of res.entries()) {
19    if (r < latestMax) {
20      res[i] = latestMax
21    }
22  }
23  return res
24}