/**
 * @param {number} x
 * @return {boolean}
 */
var isPalindrome = function(x) {
  
  if (x < 0 || x === null){
    return false;
  }
  
  let s = x.toString(10);
  
  if (s.length % 2 === 0){
    return validPalindrome(s, true);
  } else {
    return validPalindrome(s, false);
  }
};

function validPalindrome(s, even){
  
  let valid = false;
  
  //Start as same char for odd lengths
  let i = Math.floor(s.length / 2);
  let j = i;
  
  //Middle is between chars for even lengths
  if (even){
    //Start i to the left of j
    --i;
  }
  
  while(i >= 0 && j < s.length){
    if (s.charAt(i) === s.charAt(j)){
      valid = true;
      --i;
      ++j;
    } else {
      valid = false;
      break;
    }
  }
  
  return valid;
}