isPalindrome.ts

function isPalindrome(input: string): boolean {
  // Our approach to checking this input string for the quality of being a palindrome will be the following
  // 1. A single-character string is technically a Palindrome. We'll return true immediately if this is the case
  // 2. We'll split the input into an array of its characters
  // 3. We'll utilize a `while` loop to check the leftmost and rightmost characters of the input string - modifying it in-place as we do so using shift and pop
  //    There's a base-case to handle, that once we reach a length of 1, we can consider the number a palindrome
  //    If at any point, our leftmost and rightmost values are not equivalent, then the input number is not a palindrome

  // A single-character string is technically a Palindrome
  if (input.length === 1) {
    return true;
  }

  const inputSplit = input.toString().split('');

  // Our exit- condition will be once our input split has no characters left to check
  while (inputSplit.length) {
    // If we've reached a length of 1 after popping and validating
    // the leftmost and rightmost values, then we have a palindrome
    if (inputSplit.length === 1) {
      return true;
    }

    const leftmost = inputSplit.shift();
    const rightmost = inputSplit.pop();

    // The leftmost and rightmost values need to be the same for it to have been a valid palindrome
    if ((leftmost === rightmost) === false) {
      return false;
    }
  }

  // Down here, we handle the case of a input string like `abba`
  // Where we would have validated both the leftmost and rightmost
  // values, but we end up breaking out of our while-loop due to 0 characters left
  // Since we didn't encounter the failure conditions, then this had to be a palindrome
  return true;
}