function alphanumeric(obj)
{
	myarray = new Array(46);
	var numaric = obj.value;
	for(var j=0; j<numaric.length; j++)
	{
		var alphaa = numaric.charAt(j);
		var hh = alphaa.charCodeAt(0);
//		if((hh > 47 && hh<58) || (hh > 64 && hh<91) || (hh > 96 && hh<123))
		if((hh >= 32 && hh <= 125))
		{
		}
		else
		{
			alert(hh);
			alert("Please use only English characters. No Greek characters allowed.");
			obj.value = "";
			return false;
		}
	}
	return true;
}

<!-- Original:  Simon Tneoh (tneohcb@pc.jaring.my) -->

<!-- This script and many more are available free online at -->
<!-- The JavaScript Source!! http://javascript.internet.com -->

<!-- Begin
var Cards = new makeArray(8);
Cards[0] = new CardType("MasterCard", "51,52,53,54,55", "16");
var MasterCard = Cards[0];
Cards[1] = new CardType("VisaCard", "4", "13,16");
var VisaCard = Cards[1];
Cards[2] = new CardType("AmExCard", "34,37", "15");
var AmExCard = Cards[2];
Cards[3] = new CardType("DinersClubCard", "30,36,38", "14");
var DinersClubCard = Cards[3];
Cards[4] = new CardType("DiscoverCard", "6011", "16");
var DiscoverCard = Cards[4];
Cards[5] = new CardType("enRouteCard", "2014,2149", "15");
var enRouteCard = Cards[5];
Cards[6] = new CardType("JCBCard", "3088,3096,3112,3158,3337,3528", "16");
var JCBCard = Cards[6];
var LuhnCheckSum = Cards[7] = new CardType();

/*************************************************************************\
CheckCardNumber(form)
function called when users click the "check" button.
\*************************************************************************/
function CheckCardNumber(form) {
	var tmpyear;
	if (form.CardNumber.value.length == 0) {
		alert("Please enter a Card Number.");
		form.CardNumber.focus();
		return false;
	}
	if (form.ExpYear.value.length == 0) {
		alert("Please enter the Expiration Year.");
		form.ExpYear.focus();
		return false;
	}
	if (form.ExpYear.value > 96)
	tmpyear = "19" + form.ExpYear.value;
	else if (form.ExpYear.value < 21)
		tmpyear = "20" + form.ExpYear.value;
		else {
			alert("The Expiration Year is not valid.");
			return false;
		}
		tmpmonth = form.ExpMon.options[form.ExpMon.selectedIndex].value;
		// The following line doesn't work in IE3, you need to change it
		// to something like "(new CardType())...".
		// if (!CardType().isExpiryDate(tmpyear, tmpmonth)) {
		if (!(new CardType()).isExpiryDate(tmpyear, tmpmonth)) {
			alert("This card has already expired.");
			return false;
		}
		card = form.CardType.options[form.CardType.selectedIndex].value;
		var retval = eval(card + ".checkCardNumber(\"" + form.CardNumber.value +
		"\", " + tmpyear + ", " + tmpmonth + ");");
		cardname = "";
		if (retval)



		// comment this out if used on an order form
		// alert("This card number appears to be valid.");
		{return true;}


		else {
			// The cardnumber has the valid luhn checksum, but we want to know which
			// cardtype it belongs to.
			for (var n = 0; n < Cards.size; n++) {
				if (Cards[n].checkCardNumber(form.CardNumber.value, tmpyear, tmpmonth)) {
					cardname = Cards[n].getCardType();
					break;
				}
			}
			if (cardname.length > 0) {
				alert("This looks like a " + cardname + " number, not a " + card + " number.");
				return false;
			}
			else {
				alert("This card number is not valid.");
				return false;
			}
		}
	}
	/*************************************************************************\
	Object CardType([String cardtype, String rules, String len, int year,
	int month])
	cardtype    : type of card, eg: MasterCard, Visa, etc.
	rules       : rules of the cardnumber, eg: "4", "6011", "34,37".
	len         : valid length of cardnumber, eg: "16,19", "13,16".
	year        : year of expiry date.
	month       : month of expiry date.
	eg:
	var VisaCard = new CardType("Visa", "4", "16");
	var AmExCard = new CardType("AmEx", "34,37", "15");
	\*************************************************************************/
	function CardType() {
		var n;
		var argv = CardType.arguments;
		var argc = CardType.arguments.length;

		this.objname = "object CardType";

		var tmpcardtype = (argc > 0) ? argv[0] : "CardObject";
		var tmprules = (argc > 1) ? argv[1] : "0,1,2,3,4,5,6,7,8,9";
		var tmplen = (argc > 2) ? argv[2] : "13,14,15,16,19";

		this.setCardNumber = setCardNumber;  // set CardNumber method.
		this.setCardType = setCardType;  // setCardType method.
		this.setLen = setLen;  // setLen method.
		this.setRules = setRules;  // setRules method.
		this.setExpiryDate = setExpiryDate;  // setExpiryDate method.

		this.setCardType(tmpcardtype);
		this.setLen(tmplen);
		this.setRules(tmprules);
		if (argc > 4)
		this.setExpiryDate(argv[3], argv[4]);

		this.checkCardNumber = checkCardNumber;  // checkCardNumber method.
		this.getExpiryDate = getExpiryDate;  // getExpiryDate method.
		this.getCardType = getCardType;  // getCardType method.
		this.isCardNumber = isCardNumber;  // isCardNumber method.
		this.isExpiryDate = isExpiryDate;  // isExpiryDate method.
		this.luhnCheck = luhnCheck;// luhnCheck method.
		return this;
	}

	/*************************************************************************\
	boolean checkCardNumber([String cardnumber, int year, int month])
	return true if cardnumber pass the luhncheck and the expiry date is
	valid, else return false.
	\*************************************************************************/
	function checkCardNumber() {
		var argv = checkCardNumber.arguments;
		var argc = checkCardNumber.arguments.length;
		var cardnumber = (argc > 0) ? argv[0] : this.cardnumber;
		var year = (argc > 1) ? argv[1] : this.year;
		var month = (argc > 2) ? argv[2] : this.month;

		this.setCardNumber(cardnumber);
		this.setExpiryDate(year, month);

		if (!this.isCardNumber())
		return false;
		if (!this.isExpiryDate())
		return false;

		return true;
	}
	/*************************************************************************\
	String getCardType()
	return the cardtype.
	\*************************************************************************/
	function getCardType() {
		return this.cardtype;
	}
	/*************************************************************************\
	String getExpiryDate()
	return the expiry date.
	\*************************************************************************/
	function getExpiryDate() {
		return this.month + "/" + this.year;
	}
	/*************************************************************************\
	boolean isCardNumber([String cardnumber])
	return true if cardnumber pass the luhncheck and the rules, else return
	false.
	\*************************************************************************/
	function isCardNumber() {
		var argv = isCardNumber.arguments;
		var argc = isCardNumber.arguments.length;
		var cardnumber = (argc > 0) ? argv[0] : this.cardnumber;
		if (!this.luhnCheck())
		return false;

		for (var n = 0; n < this.len.size; n++)
		if (cardnumber.toString().length == this.len[n]) {
			for (var m = 0; m < this.rules.size; m++) {
				var headdigit = cardnumber.substring(0, this.rules[m].toString().length);
				if (headdigit == this.rules[m])
				return true;
			}
			return false;
		}
		return false;
	}

	/*************************************************************************\
	boolean isExpiryDate([int year, int month])
	return true if the date is a valid expiry date,
	else return false.
	\*************************************************************************/
	function isExpiryDate() {
		var argv = isExpiryDate.arguments;
		var argc = isExpiryDate.arguments.length;

		year = argc > 0 ? argv[0] : this.year;
		month = argc > 1 ? argv[1] : this.month;

		if (!isNum(year+""))
		return false;
		if (!isNum(month+""))
		return false;
		today = new Date();
		expiry = new Date(year, month);
		if (today.getTime() > expiry.getTime())
		return false;
		else
			return true;
		}

		/*************************************************************************\
		boolean isNum(String argvalue)
		return true if argvalue contains only numeric characters,
		else return false.
		\*************************************************************************/
		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;
		}

		/*************************************************************************\
		boolean luhnCheck([String CardNumber])
		return true if CardNumber pass the luhn check else return false.
		Reference: http://www.ling.nwu.edu/~sburke/pub/luhn_lib.pl
		\*************************************************************************/
		function luhnCheck() {
			var argv = luhnCheck.arguments;
			var argc = luhnCheck.arguments.length;

			var CardNumber = argc > 0 ? argv[0] : this.cardnumber;

			if (! isNum(CardNumber)) {
				return false;
			}

			var no_digit = CardNumber.length;
			var oddoeven = no_digit & 1;
			var sum = 0;

			for (var count = 0; count < no_digit; count++) {
				var digit = parseInt(CardNumber.charAt(count));
				if (!((count & 1) ^ oddoeven)) {
					digit *= 2;
					if (digit > 9)
					digit -= 9;
				}
				sum += digit;
			}
			if (sum % 10 == 0)
			return true;
			else
				return false;
			}

			/*************************************************************************\
			ArrayObject makeArray(int size)
			return the array object in the size specified.
			\*************************************************************************/
			function makeArray(size) {
				this.size = size;
				return this;
			}

			/*************************************************************************\
			CardType setCardNumber(cardnumber)
			return the CardType object.
			\*************************************************************************/
			function setCardNumber(cardnumber) {
				this.cardnumber = cardnumber;
				return this;
			}

			/*************************************************************************\
			CardType setCardType(cardtype)
			return the CardType object.
			\*************************************************************************/
			function setCardType(cardtype) {
				this.cardtype = cardtype;
				return this;
			}

			/*************************************************************************\
			CardType setExpiryDate(year, month)
			return the CardType object.
			\*************************************************************************/
			function setExpiryDate(year, month) {
				this.year = year;
				this.month = month;
				return this;
			}

			/*************************************************************************\
			CardType setLen(len)
			return the CardType object.
			\*************************************************************************/
			function setLen(len) {
				// Create the len array.
				if (len.length == 0 || len == null)
				len = "13,14,15,16,19";

				var tmplen = len;
				n = 1;
				while (tmplen.indexOf(",") != -1) {
					tmplen = tmplen.substring(tmplen.indexOf(",") + 1, tmplen.length);
					n++;
				}
				this.len = new makeArray(n);
				n = 0;
				while (len.indexOf(",") != -1) {
					var tmpstr = len.substring(0, len.indexOf(","));
					this.len[n] = tmpstr;
					len = len.substring(len.indexOf(",") + 1, len.length);
					n++;
				}
				this.len[n] = len;
				return this;
			}

			/*************************************************************************\
			CardType setRules()
			return the CardType object.
			\*************************************************************************/
			function setRules(rules) {
				// Create the rules array.
				if (rules.length == 0 || rules == null)
				rules = "0,1,2,3,4,5,6,7,8,9";

				var tmprules = rules;
				n = 1;
				while (tmprules.indexOf(",") != -1) {
					tmprules = tmprules.substring(tmprules.indexOf(",") + 1, tmprules.length);
					n++;
				}
				this.rules = new makeArray(n);
				n = 0;
				while (rules.indexOf(",") != -1) {
					var tmpstr = rules.substring(0, rules.indexOf(","));
					this.rules[n] = tmpstr;
					rules = rules.substring(rules.indexOf(",") + 1, rules.length);
					n++;
				}
				this.rules[n] = rules;
				return this;
			}
			//  End -->