Project Euler . Problem 4 . Largest palindrome product : A palindromic number reads the same both ways. The largest palindrome made from the product of two 2-digit numbers is 9009 = 91 × 99. Find the largest palindrome made from the product of two 3-digit numbers.

projecteuler4.js

var check = function() {
  rtnNum = a*b;
  console.log(a + ' * ' + b + ' = ' + rtnNum);
  strAns = String(rtnNum);
  flag = true;
  // check
  for (var x=0; x<strAns.length/2; x++) {
    //console.log('strAns[x] : ' + strAns[x]);
    //console.log('strAns[strAns.length-(x+1)] : ' + strAns[strAns.length-(x+1)]);
    if (strAns[x] != strAns[strAns.length-(x+1)]) { flag = false; return 0; }
  }
  return rtnNum;
};
var DEFAULTNUM = 999;
var a = DEFAULTNUM;
var b = DEFAULTNUM;
var ans = 0;
var flag;
for (; a>=(DEFAULTNUM/1.1); a--) {
  tmp = check();
  if (ans < tmp) ans = tmp;

  for (; b>=(DEFAULTNUM/1.1); b--) {
    tmp = check();
    if (ans < tmp) ans = tmp;
  }
  b = a;
}
console.log(ans);