I’m working on a subscription page which needs to identify the type of the entered credit card number, and display a logo accordingly. I came up with the following script to ID the card:


// get entered cc_number using jQuery
cc_number = $("#cc_number").val();


// remove spaces and hyphens
cc_number = cc_number.replace(/[ -]/g,"");


// initially the card type is unknown
cardtype = '';
$j("#cc_type").val("");


// define card names and their matching patterns
ccArray = {"visa" : "^4[0-9]{12}(?:[0-9]{3})?$",
"mastercard" : "^5[1-5][0-9]{14}$",
"discover" : "^6011[0-9]{12}$",
"amex" : "^3[47][0-9]{13}$"};


// identify the card type
for (key in ccArray) {
regex = new RegExp(ccArray[key]);
if (regex.test(cc_number)) {
cardtype = key;
break;
}
}

I validate the card number next (JS routine available elsewhere on the web), and if that's ok, display the logo using the card type.