CFLib.org – Common Function Library Project

Description:
This is an implementation of the Luhn algorithm or Luhn formula, also known as the "modulus 10" or "mod 10" algorithm. It calculates the check digit for a number and appends it to the end of the orignal string. For more details check out http://en.wikipedia.org/wiki/Luhn_algorithm

Return Values:
Returns a number.

Example:

#createMod10(123456789)#

Parameters:

Full UDF Source:

/**
 * Implementation of Luhn algorithm or Mod10.
 * v2 fix by Mike Causer
 * 
 * @param number      Value to format. (Required)
 * @return Returns a number. 
 * @author Lucas Sherwood (lucas@thebitbucket.net) 
 * @version 2, September 9, 2009 
 */
function createMod10(number) {
    // this function generates the check digit and appends it to the orignal string
    var nDigits = len(arguments.number);
    var sum = 0;
    var i=0;
    var digit = "";
    var checkdigit = 0;
    for (i=0; i LT nDigits; i=i+1) {
        digit = mid(arguments.number, nDigits-i, 1);
        if(NOT (i MOD 2)) {
            digit = digit+digit;
            // check to see if we should add
            if(len(digit) gt 1) {
                digit = left(digit,1) + right(digit,1);
            }
        }
        checkdigit = checkdigit + digit;
    }
    // divid by 10 and subtract from 10
    checkdigit = 10 - (checkdigit mod 10);
    return arguments.number & right( checkdigit, 1 );
}