// JScript File

function CreditCardValidation (sender, args)
{
  var cardNumber = document.getElementById(objCardNumber).value;
  var cardType = document.getElementById(objCardType)[document.getElementById(objCardType).selectedIndex].value;  
  var isValid = false;
  var ccCheckRegExp = /[^\d ]/;
  isValid = !ccCheckRegExp.test(cardNumber);

  if (isValid)
  {
    var cardNumbersOnly = cardNumber.replace(/ /g,"");
    var cardNumberLength = cardNumbersOnly.length;
    var lengthIsValid = false;
    var prefixIsValid = false;
    var prefixRegExp;

    switch(cardType)
    {
      case "mastercard":
        lengthIsValid = (cardNumberLength == 16);
        prefixRegExp = /^5[1-5]/;
        break;

      case "visa":
        lengthIsValid = (cardNumberLength == 16 || cardNumberLength == 13);
        prefixRegExp = /^4/;
        break;

      case "amex":
        lengthIsValid = (cardNumberLength == 15);
        prefixRegExp = /^3(4|7)/;
        break;

      default:
        prefixRegExp = /^$/;
        alert("Card type not found");
    }

    prefixIsValid = prefixRegExp.test(cardNumbersOnly);
    isValid = prefixIsValid && lengthIsValid;
  }

  if (isValid)
  {
    var numberProduct;
    var numberProductDigitIndex;
    var checkSumTotal = 0;

    for (digitCounter = cardNumberLength - 1; 
      digitCounter >= 0; 
      digitCounter--)
    {
      checkSumTotal += parseInt (cardNumbersOnly.charAt(digitCounter));
      digitCounter--;
      numberProduct = String((cardNumbersOnly.charAt(digitCounter) * 2));
      for (var productDigitCounter = 0;
        productDigitCounter < numberProduct.length; 
        productDigitCounter++)
      {
        checkSumTotal += 
          parseInt(numberProduct.charAt(productDigitCounter));
      }
    }

    isValid = (checkSumTotal % 10 == 0);
  }

  args.IsValid = isValid;
}