function isValidCardNumber (strNum) 
{
   var nCheck = 0;
   var nDigit = 0;
   var bEven  = false;
   
   for (n = strNum.length - 1; n >= 0; n--) 
   {
      var cDigit = strNum.charAt (n);
      if (isDigit (cDigit))
      {
         var nDigit = parseInt(cDigit, 10);
         if (bEven)
         {
            if ((nDigit *= 2) > 9)
               nDigit -= 9;
         }
         nCheck += nDigit;
         bEven = ! bEven;
      }
      else if (cDigit != ' ' && cDigit != '.' && cDigit != '-')
      {
         return false;
      }
   }
   return (nCheck % 10) == 0;
}

function isExpiryDate(year, month) { 
	today = new Date();
	expiry = new Date(year, month);
	if (today.getTime() > expiry.getTime())	return false;
	else return true;
	}
function isNum(argvalue) {
	argvalue = argvalue.toString();
	
	if (argvalue.length == 0)
	return false;
	
	for (var n = 0; n < argvalue.length; n++)
	if (argvalue.substring(n, n+1) < "0" || argvalue.substring(n, n+1) > "9")
	return false;
	
	return true;
	}

function isDigit (c)
{
   var strAllowed = "1234567890";
   return (strAllowed.indexOf (c) != -1);
}
function isCardTypeCorrect (strNum, type)
{
   var nLen = 0;
   for (n = 0; n < strNum.length; n++)
   {
      if (isDigit (strNum.substring (n,n+1)))
         ++nLen;
   }
   
   if (type == 'V')
      return ((strNum.substring(0,1) == '4') && (nLen == 13 || nLen == 16));
   else if (type == 'A')
      return ((strNum.substring(0,2) == '34' || strNum.substring(0,2) == '37') && (nLen == 15));
   else if (type == 'M')
      return ((strNum.substring(0,2) == '51' || strNum.substring(0,2) == '52'
              || strNum.substring(0,2) == '53' || strNum.substring(0,2) == '54'
              || strNum.substring(0,2) == '55') && (nLen == 16));
	else if (type == 'D')
      return ((strNum.substring(0,4) == '6011' || strNum.substring(0,3) == '622'
              || strNum.substring(0,2) == '64' || strNum.substring(0,2) == '65') && (nLen == 16));	  
   else
      return false;
   
}