1
var reverseOnlyLetters = function (s) {
2
  let valid = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ";
3
  let arr = s.split("");
4

5
  let r = arr.length - 1;
6
  let l = 0;
7

8
  while (l < r) {
9
    while (!valid.includes(arr[l]) && l < r) {
10
      l++;
11
      continue;
12
    }
13

14
    while (!valid.includes(arr[r]) && l < r) {
15
      r--;
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      continue;
17
    }
18

19
    if (l >= r) break;
20

21
    [arr[l], arr[r]] = [arr[r], arr[l]];
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    l++;
23
    r--;
24
  }
25

26
  return arr.join("");
27
};