// Card Number = Credit Card number
// Card name = Card Type
function checkCreditCard (cardnumber, cardname) {
// Array to hold the permitted card characteristics
var cards = new Array();
// Define the cards we support. You may add addtional card types as follows.
// Name: As in the selection box of the form - must be same as user's
// Length: List of possible valid lengths of the card number for the card
// prefixes: List of possible prefixes for the card
// checkdigit: Boolean to say whether there is a check digit
cards [0] = {name: "Visa",
length: "13,16",
prefixes: "4",
checkdigit: true};
cards [1] = {name: "MasterCard",
length: "16",
prefixes: "51,52,53,54,55",
checkdigit: true};
cards [2] = {name: "DinersClub",
length: "14,16",
prefixes: "305,36,38,54,55",
checkdigit: true};
cards [3] = {name: "CarteBlanche",
length: "14",
prefixes: "300,301,302,303,304,305",
checkdigit: true};
cards [4] = {name: "AmEx",
length: "15",
prefixes: "34,37",
checkdigit: true};
cards [5] = {name: "Discover",
length: "16",
prefixes: "6011,622,64,65",
checkdigit: true};
cards [6] = {name: "JCB",
length: "16",
prefixes: "35",
checkdigit: true};
cards [7] = {name: "enRoute",
length: "15",
prefixes: "2014,2149",
checkdigit: true};
cards [8] = {name: "Solo",
length: "16,18,19",
prefixes: "6334,6767",
checkdigit: true};
cards [9] = {name: "Switch",
length: "16,18,19",
prefixes: "4903,4905,4911,4936,564182,633110,6333,6759",
checkdigit: true};
cards [10] = {name: "Maestro",
length: "12,13,14,15,16,18,19",
prefixes: "5018,5020,5038,6304,6759,6761",
checkdigit: true};
cards [11] = {name: "VisaElectron",
length: "16",
prefixes: "417500,4917,4913,4508,4844",
checkdigit: true};
cards [12] = {name: "LaserCard",
length: "16,17,18,19",
prefixes: "6304,6706,6771,6709",
checkdigit: true};
// Establish card type
var cardType = -1;
for (var i=0; i<cards.length; i++) {
// See if it is this card (ignoring the case of the string)
if (cardname.toLowerCase () == cards[i].name.toLowerCase()) {
cardType = i;
break;
}
}
// If card type not found, report an error
if (cardType == -1) {
ccErrorNo = 0;
return false;
}
// Ensure that the user has provided a credit card number
if (cardnumber.length == 0) {
ccErrorNo = 1;
return false;
}
// Now remove any spaces from the credit card number
cardnumber = cardnumber.replace (/\s/g, "");
// Check that the number is numeric
var cardNo = cardnumber
var cardexp = /^[0-9]{13,19}$/;
if (!cardexp.exec(cardNo)) {
ccErrorNo = 2;
return false;
}
// Now check the modulus 10 check digit - if required
if (cards[cardType].checkdigit) {
var checksum = 0; // running checksum total
var mychar = ""; // next char to process
var j = 1; // takes value of 1 or 2
// Process each digit one by one starting at the right
var calc;
for (i = cardNo.length - 1; i >= 0; i--) {
// Extract the next digit and multiply by 1 or 2 on alternative digits.
calc = Number(cardNo.charAt(i)) * j;
// If the result is in two digits add 1 to the checksum total
if (calc > 9) {
checksum = checksum + 1;
calc = calc - 10;
}
// Add the units element to the checksum total
checksum = checksum + calc;
// Switch the value of j
if (j ==1) {j = 2} else {j = 1};
}
// All done - if checksum is divisible by 10, it is a valid modulus 10.
// If not, report an error.
if (checksum % 10 != 0) {
ccErrorNo = 3;
return false;
}
}
// The following are the card-specific checks we undertake.
var LengthValid = false;
var PrefixValid = false;
var undefined;
// We use these for holding the valid lengths and prefixes of a card type
var prefix = new Array ();
var lengths = new Array ();
// Load an array with the valid prefixes for this card
prefix = cards[cardType].prefixes.split(",");
// Now see if any of them match what we have in the card number
for (i=0; i<prefix.length; i++) {
var exp = new RegExp ("^" + prefix[i]);
if (exp.test (cardNo)) PrefixValid = true;
}
// If it isn't a valid prefix there's no point at looking at the length
if (!PrefixValid) {
ccErrorNo = 3;
return false;
}
// See if the length is valid for this card
lengths = cards[cardType].length.split(",");
for (j=0; j<lengths.length; j++) {
if (cardNo.length == lengths[j]) LengthValid = true;
}
// See if all is OK by seeing if the length was valid. We only check the length if all else was
// hunky dory.
if (!LengthValid) {
ccErrorNo = 4;
return false;
};
// The credit card is in the required format.
return true;
}
