Javascript: Credit card validation

Here’s a quick Javascript I wrote to validate (The 4 major American) credit card numbers, based on this post by Harrell W. Stiles.

Validate a credit card number with Javascript.

View the source on that page to grab the code, here are the two main functions as a quick reference:

function get_cc_type(n){
var n2 = n.substr(0,2);
var n4 = n.substr(0,4);
var n1 = n.substr(0,1);
var l = n.length

if(n4 == “6011″ && l == 16){
return “discover”;
} else if(n1 == “4″ && l > 12 && l < 17){
return “visa”;
} else if(n2 == “51″ || n2 == “52″ || n2 == “53″ || n2 == “54″ || n2 == “55″ && l == 16){
return “mastercard”;
} else if(n2 == “34″ || n2 == “37″ && l == 15){
return “american_express”;
} else {
return “unknown”;
}
}

function is_valid_cc_number(n){
var toggle = 0;
var total = 0;
n = n.split(”").reverse();
for(i=0;i<n.length;i++){
if(toggle == 0){
val = n[i];
toggle = 1;
} else {
val = n[i] * 2;
if(val > 9){
tempVal = val.toString().split(”");
val = parseInt(tempVal[0]) + parseInt(tempVal[1]);
}
toggle = 0;
}
total = parseInt(total) + parseInt(val);
}

if(total % 10 === 0){
return true;
} else {
return false;
}
}

A copy of the original post follows.

Credit Card Validation - Check Digits

This document outlines procedures and algorithms for Verifying
the accuracy and validity of credit card numbers. Most credit
card numbers are encoded with a “Check Digit”. A check
digit is a digit added to a number (either at the end or the beginning)
that validates the authenticity of the number. A simple algorithm
is applied to the other digits of the number which yields the
check digit. By running the algorithm, and comparing the check
digit you get from the algorithm with the check digit encoded
with the credit card number, you can verify that you have correctly
read all of the digits and that they make a valid combination.

Possible uses for this information:

• When a user has keyed in a credit card number (or scanned
  it) and you want to validate it before sending it our for debit
  authorization.
• When issuing cards, say an affinity card, you might want to
  add a check digit using the MOD 10 method.

1.Prefix, Length, and Check Digit Criteria

Here is a table outlining the major credit cards that you might
want to validate.

2. LUHN Formula (Mod 10) for Validation of Primary Account
Number

The following steps are required to validate the primary account
number:

Step 1: Double the value of alternate digits of the primary
account number beginning with the second digit from the right
(the first right–hand digit is the check digit.)

Step 2: Add the individual digits comprising the products
obtained in Step 1 to each of the unaffected digits in the original
number.

Step 3: The total obtained in Step 2 must be a number ending
in zero (30, 40, 50, etc.) for the account number to be validated.

For example, to validate the primary account number 49927398716:

Step 1:

        4 9 9 2 7 3 9 8 7 1 6

         x2  x2  x2  x2  x2

------------------------------

         18   4   6  16   2

Step 2: 4 +(1+8)+ 9 + (4) + 7 + (6) + 9 +(1+6) + 7 + (2)
+ 6

Step 3: Sum = 70 : Card number is validated

Note: Card is valid because the 70/10 yields no remainder.

The great folks at ICVERIFY
are the original source of this data, I only formatted it in HTML.

If you are in the market, I wrote a set of FoxPro

modules for Windows/Dos that interface nicely with ICVERIFY
in a multi-user LAN setup. You just set up ICVERIFY
on a single station, and all stations on the LAN can authorize
credit cards with a single FOXBASE function call. Of course, you
have to license ICVERIFY by the node, but it is very reasonable.
I also wrote a couple of simple functions to perform pre-authorization,
card screening, etc.

Here is a Microsoft Excel worksheet
that will validate a number for you (useful for understanding
the algorithm, it is in a .ZIP compressed format)

Horace Vallas made a NeoWebScript (Tcl really) procedure that
implements it.

Check it out at https://enterprise.neosoft.com/secureforms/hav/

Because I get at least a letter a week regarding this routine,
here are some additional helpful notes:

Make sure that you:

1. have started with the rightmost digit (including the check
   digit) (figure odd and even based upon the rightmost digit being
   odd, regardless of the length of the Credit Card.) ALWAYS work
   right to left.
2. the check digit counts as digit #1 (assuming that the rightmost
   digit is the check digit) and is not doubled
3. double every second digit (starting with digit # 2 from the
   right)
4. remember that when you double a number over 4, (6 for example)
   you don’t add the result to your total, but rather the sum of
   the digits of the result (in the above example 6*2=12 so you would
   add 1+2 to your total (not 12).
5. always include the Visa or M/C/ prefix.

PHPBB3 - Delete spam users and posts

One particular forum that I administrate recently had a problem with an influx of spam users and posts.  We needed a solution but until I could come up with one we needed a quick way to get rid of the trash they were posting on our public forums, so I wrote this script.  

The script accepts a username as input, and it will remove every trace of that user from the PHPBB database.  It deletes their username, bans their username and IP Address, removes any posts and/or topics created by them, and corrects the ‘last post by’ on each forum by removing them.

Feel free to use this script if you like, but be aware it’s very dangerous as it’s directly editing the PHPBB3 database tables.  The only configuration you need to supply is the database name, hostname, and auth credentials.  The script also assumes you used the default table prefix (phpbb_) when installing.

Code: http://ryanbrotherton.pastebin.com/f2dd5c4a3

JavaScript: Image Rotator

One day I found myself in need of an image rotator, but instead of grabbing a pre-made script I decided to write my own.  Why re-invent the wheel you ask?  Because I like to learn and I love JavaScript, I don’t get to write custom JavaScript nearly enough.  Also, to better understand how this particular wheel works.  I want to re-write this eventually  to remove the dependency on Scriptaculous.

I shouldn’t have to say this but if you want to use it, you’re free to use it for any purpose.

Dependencies: Scriptaculous - For the fading effect.

Code: http://ryanbrotherton.pastebin.com/f1cc2203c

10 digit decimal IP addresses - How to

There is a little known quirk in the Internet Explorer and Firefox browsers.  Here’s an example link to Google: http://1249710995.  If clicking it doesn’t work for you, copy and paste it into IE6 or 7 or FF3. (I haven’t tested any other browsers except for Opera and Chrome, neither of them work.)

I wrote a quick converter in PHP, you can play with it here and download the source code on the same page.

How to: Convert each octet of an IPv4 address to hex and concatenate the hex values into one giant number. Convert the number back to decimal and you have the 10 digit number.

Quick reference conversion functions:

IP Address to 10 digit:

function toTen($i){
$a = explode(”.”,$i);
$g1 = $a[0];
$g2 = $a[1];
$g3 = $a[2];
$g4 = $a[3];

$g1 *= 16777216;
$g2 *= 65536;
$g3 *= 256;

return $g1 + $g2 + $g3 + $g4;
}

10 digit back to IP:

function toIP($i){
$i = dechex($i+0);
$g1 = hexdec(substr($i,0,2));
$g2 = hexdec(substr($i,2,2));
$g3 = hexdec(substr($i,4,2));
$g4 = hexdec(substr($i,6,2));

return $g1.”.”.$g2.”.”.$g3.”.”.$g4;
}

Why: Anonymity.  I can’t think of a use for this that isn’t potentially malicious.  It could be used by malware to trick users into going to an unfriendly url, and bypass blacklisted domain names in spam filters.

I’m sure the feature is put there for a reason, I’m just not sure what it is.  Got any ideas?