is-palyndrome.js

const palyndrome = 'laal';

function reverseString(str) {
  return Array.prototype.reduceRight.call(str, (acc, newElement) => 	 
    acc + newElement, '');
}

function isPalyndrome(str) {
  const length = str.length;
  if (length === 0 || length === 1) {
    return true;
  } else if (length % 2 === 0) {
    const middle = length / 2;
    return str.substr(0, middle) === reverseString(str.substr(middle, length));
  } else {
    const middle = Math.floor(length / 2);
    return str.substr(0, middle) === reverseString(str.substr(middle + 1, length));
  }
}

console.log(isPalyndrome(palyndrome));