Validate Credit Card Number

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This checks the credit card number against known truths of credit card numbers.

Body Code:

<script language="javascript">
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 key in Card Number.");
    form.CardNumber.focus();
    return;
  }
  if (form.ExpYear.value.length == 0) {
    alert("Please key in Expiry Year.");
    form.ExpYear.focus();
    return;
  }
  if (form.ExpYear.value > 96)
    tmpyear = "19" + form.ExpYear.value;
  else if (form.ExpYear.value < 21)
    tmpyear = "20" + form.ExpYear.value;
  else {
    alert("bad year");
    return;
  }
  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("expiry date passed already.");
    return;
  }
  card = form.CardType.options[form.CardType.selectedIndex].value;
  var retval = eval(card + ".checkCardNumber("" + form.CardNumber.value +
        "", " + tmpyear + ", " + tmpmonth + ");");

  cardname = "";
  if (retval)
    // The cardnumber has the valid luhn checksum and matches the
    // cardtype's rule.
    alert("correct");
  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's " + cardname + " number, not " + card + " number.");
    }
    else {
      alert("This's not a card number.");
    }
  }
}

/*************************************************************************
   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";

  // set CardNumber method.
  this.setCardNumber = setCardNumber;

  // setCardType method.
  this.setCardType = setCardType;

  // setLen method.
  this.setLen = setLen;

  // setRules method.
  this.setRules = setRules;

  // setExpiryDate method.
  this.setExpiryDate = setExpiryDate;

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

  // checkCardNumber method.
  this.checkCardNumber = checkCardNumber;

  // getExpiryDate method.
  this.getExpiryDate = getExpiryDate;

  // getCardType method.
  this.getCardType = getCardType;

  // isCardNumber method.
  this.isCardNumber = isCardNumber;

  // isExpiryDate method.
  this.isExpiryDate = isExpiryDate;

  // luhnCheck method.
  this.luhnCheck = luhnCheck;

  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;
}

</script>
<h2>Credit Card Number Validator</h2>
<hr>
<blockquote>

<font color="#ff0000">Alert!
Please do not use a real card number and valid expiry date to test. If you
really want to do it, please check the source first, make sure it will not
submit the card number.<br></font>
<form name="ThisForm">
Card Number: <input name="CardNumber" size="16" maxlength="19"><br>
Card Type:
<select name="CardType">
<option value="MasterCard">MasterCard
<option value="VisaCard">Visa
<option value="AmExCard">AmEx
<option value="DinersClubCard">Diners Club
<option value="DiscoverCard">Discover
<option value="enRouteCard">enRoute
<option value="JCBCard">JCB
<option value="LuhnCheckSum">luhn check only
</select>
<br>
Expiry Date: Month
<select name="ExpMon">
<option value="1" selected>1
<option value="2">2
<option value="3">3
<option value="4">4
<option value="5">5
<option value="6">6
<option value="7">7
<option value="8">8
<option value="9">9
<option value="10">10
<option value="11">11
<option value="12">12
</select>
Year <input name="ExpYear" size="2" maxlength="2">(Range: 1997~2020)<br>
<input type="button" value="Check" OnClick="CheckCardNumber(this.form)"><br>
</form>

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