Discover if a word is a palindrome, using JavaScript built-in array methods, manually reversing the string array or moving two pointers.

is-palindrome.ts

// $ bun init
// $ bun run is-palindrome.ts

function isPalindrome(word: string) {
  return word === word.split('').reverse().join('');
}

console.log('[v1] Array<string>.reverse');
console.log('renner', isPalindrome('renner'));
console.log('cachorro', isPalindrome('cachorro'));
console.log('kaiak', isPalindrome('kaiak'));

// ------

function reverseLetters(letters: string[]) {
  let reversedLetters: string[] = [];

  for (let i = 0; i < letters.length; i++) {
    reversedLetters[i] = letters[letters.length - 1 - i] as string;
  }

  return reversedLetters;
}

function isPalindromeV2(word: string) {
  return word === reverseLetters(word.split('')).join('');
}

console.log('[v2] Manually reverse array');
console.log('renner', isPalindromeV2('renner'));
console.log('cachorro', isPalindromeV2('cachorro'));
console.log('kaiak', isPalindromeV2('kaiak'));

// ------

function isPalindromeV3(word: string) {
  let left = 0;
  let right = word.length - 1;

  while (left < right) {
    if (word[left] !== word[right]) {
      return false;
    }

    left++;
    right--;
  }

  return true;
}

console.log('[v3] two pointers');
console.log('renner', isPalindromeV3('renner'));
console.log('cachorro', isPalindromeV3('cachorro'));
console.log('kaiak', isPalindromeV3('kaiak'));