Break a Palindrome LeetCode solution in JavaScript

1
var breakPalindrome = function (palindrome) {
2
  // domain n / 2 k pehlay
3
  palindrome = palindrome.split("");
4
  const len = palindrome.length;
5
  if (len == 1) return "";
6
  const domain = Math.floor(len / 2);
7
  let firstNonAChar = -1,
8
    lastAChar = -1;
9
  for (let i = 0; i < domain; i++) {
10
    if (palindrome[i] != "a") {
11
      firstNonAChar = i;
12
      break;
13
    }
14
  }
15
  if (firstNonAChar == -1) {
16
    palindrome[len - 1] = "b";
17
  } else palindrome[firstNonAChar] = "a";
18
  return palindrome.join("");
19
};