//http://www.beachnet.com/~hstiles/cardtype.html
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 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 == 'Visa')
		return ((strNum.substring(0, 1) == '4')
			&& (nLen == 13 || nLen == 16));
	else if (type == 'Amex')
		return ((strNum.substring(0, 2) == '34'
			 || strNum.substring(0, 2) == '37')
			&& (nLen == 15));
	else if (type == 'Master Card')
		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
		return false;

}