LUHN-STRING

A library to generate alphanumeric strings that end with a checksum "digit". Digits in the string are in the range 0-9B-DF-HJ-NP-TV-XZ. All uppercase.

Changed in v1.2.0 > provide your own character sequence using var cardLuhn = require('luhn-string')('0123456789'); where '0123456789' is the valid character sequence for the strings you want to generate. Call on the generated object as always.

Change log

1.2.0. Rather than having to send the valid caharacters sequence for every call, the main Luhn Object has been upgraded to be a factory for LuhnObjects. Check sample.js for updated samples

1.1.0. All functions allow you specify a string of valid characters in case you do not want the default of 0-9A-Z excluding vowels and Y. Callbacks can still be sent. All results are still Uppercase. Note that the characters must be in same order when you are validating. A random string generated with sequence '0123456789' will not validate correctly against sequence '9876543210'.

Advantages

1. Strings have a checksum character at the end.
2. Avoid Bad words in generated string by removing A,E,I,O,U,Y
3. Random strings are cryptographically generated (dependent on node's crypto library)
4. Provide your own character sequence

Installation

npm install luhn-string -save

Usage

var Luhn = require('luhn-string');

// to generate a 16-digit checksummed string
var str = Luhn.random(16);
console.log(str);

// to generate a 16-digit checksummed string with 0123456789 as sequence
// Method 1
var res = Luhn.random(16, '0123456789');
console.log(res);
console.log(Luhn.check(res, '0123456789'));

// Method 2
var creator = new Luhn('0123456789');
res = creator.random(16);
console.log(res);
console.log(creator.check(res));


// to test a string for checksum validity
var chk = Luhn.check('30MFLRQDVCFQ9SK1');
var valid = chk.result;
var validityerror = chk.error;

// Use callbacks
Luhn.random(16, function(error, result){
  if(error){
    // do something with error...
    return;
  }
  console.log(result);
});

Luhn.check('LH989002BW3P', function(error, result){
  if(error){
    // do something with error...
    return;
  }
  console.log(result); // true or false
});

Extras

The library uses a crypto function to generate random strings. This is Exposed for your use in 2 forms:

1. cryptoRandomAsciiString(length)

returns a truly random ascii string of length length

2 cryptoRandomString(length, chars)

returns a truly random ascii string of length length, picking characters in string chars

3 addChecksum(str, callback)

checks that str contains valid characters and appends a checksum character at its end. Should be used in callback fashion. Returns null if there is an error otherwise.