logic.js

document.getElementById("check").onclick = function () {
  let getInput = document.getElementById("getInput").value;

  try {
    isPalindromeBuiltIn(getInput);
    isPalindrome(getInput);
  } catch (err) {
    console.error(err.message);
  }
};

function isPalindromeBuiltIn(string) {
  const sanitized = string.toLowerCase().match(/[a-z0-9]/g, "");
  return sanitized.join("") === sanitized.reverse().join("")
    ? alert("It is a palindrome. (Built In Function)")
    : alert("It is not a palindrome. (Built In Function)");
}
// spread operator and reverse() will reverse your string every whitespace, so you dont need loop the string inside array of reversed string just join it instead.

function isPalindrome(string) {
  const sanitized = string
    .toLowerCase()
    .match(/[a-z0-9]/g, "")
    .join("");

  for (
    var reverseChar = 0;
    reverseChar < Math.floor(sanitized.length / 2);
    reverseChar++
  ) {
    //only need to run for half the string length
    if (
      sanitized.charAt(reverseChar) !==
      sanitized.charAt(sanitized.length - reverseChar - 1)
    ) {
      // uses !== to compare characters one-by-one from the beginning and end
      return alert("It is not a palindrome.");
    }
  }

  return alert("It is a palindrome.");
}

// console.log(
//   isPalindrome("Sator Arepo Tenet Opera Rotas."), // true
//   isPalindrome("Aku suka rajawali, bapak. Apabila wajar, aku suka."), // true
//   isPalindrome("Kasur ini rusak."), // true
//   isPalindrome("Tasupi dan Tika sama-sama sakit nadi pusat."), // true
//   isPalindrome("Pada hari minggu, apakah aku turut ayah ke kota?") // false
// );