Spoiler Alert: Project Euler 4

euler4.js

var getPalindrome = function(num) {
  var str = num.toString().split(''),
    len = str.length,
    half = len / 2;

  for(var i = 0; i < half; i++) {
    str[len - 1 - i] = str[i];
  }

  return parseInt(str.join(''), 10);
}

var findLargestPalindrome = function(numDigs) {
  var dig1 = Math.pow(10, numDigs) - 1,
      minDig = Math.floor(dig1/10),
      largestProduct = Math.pow(dig1, 2), // Find largest product of 2 3-digits number
      largestPalindrome = getPalindrome(largestProduct),
      len = largestPalindrome.toString().length / 2;

  while(largestPalindrome > 0) {
    // console.log(largestPalindrome);

    for(var i = dig1; i > minDig; i--) {
      var division,
          validPalindrome = !(largestPalindrome % i)
                            && (division = largestPalindrome / i) > minDig
                            && division <= dig1;

      // console.log(i, division, validPalindrome);

      if(validPalindrome) {
        console.log(i, division, largestPalindrome);
        return largestPalindrome;
      }
    }

    // this was not a valid palindrome (not divisible by 2 n-digits digits)
    // find the next one
    len = largestPalindrome.toString().length / 2;
    largestPalindrome -= Math.pow(10, len);
    // and find the new palindrome
    largestPalindrome = getPalindrome(largestPalindrome);
  }

  return false;
}

console.log(findLargestPalindrome(3));