Task: palindrome

First I settle the rules: do we ignore case, spaces and punctuation? Below we compare all characters and ignore case only.

function isPalindrome(text) {
  const chars = Array.from(text.toLowerCase());
  for (let left = 0, right = chars.length - 1; left < right; left++, right--) {
    if (chars[left] !== chars[right]) return 0;
  }
  return true;
}
isPalindrome('Kayak'); // true
isPalindrome('React'); // 0

To be precise: following the task's unusual contract, we return true or 0; a normal API would be better off returning a consistent boolean. Time O(n), memory O(n) for the array of code points. Complex graphemes need extra handling.