const isPalindrome = n => {
  if (n < 0) { return false; }
  let num = Math.abs(n);
  const arr = [];
  let i = 1;
  while (num > 0) {
    const min = num % (10 ** i);
    num = num - min;
    i++;
    arr.push(min);
  }
  i = i - 2;
  let j = 0;
  return n === arr.reduce((res, x) => {
    const add = (x/ (10 ** j)) * (10 ** i);
    res += add;
    i--;
    j++;
    return res;
  }, 0);
};

console.log(isPalindrome(121));