Palindrome Check

check-palindrome.js

String.prototype.isPalindrome = function(charIndex = 0) {
  const stringLength = this.length;
  const charIndexFromBehind = stringLength - charIndex - 1;
  const isCharSame = this[charIndex] === this[charIndexFromBehind];
  if (!isCharSame) {
    return false;
  }
  const isIndexSame = charIndex === charIndexFromBehind;
  if (isIndexSame) {
    return true;
  }
  const nextCharIndex = charIndex + 1
  return this.isPalindrome(nextCharIndex);
}

String.prototype.reverse = function() {
  return this.split('').reverse().join('');
}

String.prototype.getMiddleCharIndex = function() {
  return Math.round(this.length/2);
}

String.prototype.middleSplit = function() {
  firstHalf = this.substr(0, this.getMiddleCharIndex());
  secondHalf = this.substr(this.getMiddleCharIndex() - 1, this.length);
  return [firstHalf, secondHalf];
}

String.prototype.isLapindrome = function() {
  const [firstHalf, secondHalf] = this.middleSplit();
  return firstHalf === secondHalf.reverse();
}

const inputStrings = ['mom', 'test', 'dad', 'factor', 'wise', 'racecar'];

inputStrings.map(inputString => {
  console.log(`Q: Is '${inputString}' is palindrome?'`)
  console.log(`A: ${inputString.isPalindrome() ? 'Yes' : 'No'}!'`);
  console.log('--------');
  console.log(`Q: Is '${inputString}' is lapindrome?'`)
  console.log(`A: ${inputString.isLapindrome() ? 'Yes' : 'No'}!'`);
  console.log('========');
});