AR Script: alternate page rename

  if (index % 2 == 0)
  {return "Hoja " + zpad(Math.round((index - 1) / 2) + 100, 3) + " Verso"}
  else
  {return "Hoja " + zpad(Math.round((index - 1) / 2) + 100, 3) + " Anverso"}

// Function that add leading zeros to any string
function zpad(num, nb_digits) {
  sNum = num.toString()
    if (sNum.length < nb_digits) { return (Array(nb_digits - sNum.length + 1).join('0') + sNum); }
    else { return sNum; }
}