Implementation of Perl's Algorithm::CouponCode for NodeJS
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Latest commit abde336 Nov 19, 2016

An implementation of Perl's Algorithm::CouponCode for NodeJS. Thanks to Grant for the inspiration. :)

Note: this package is considered stable, hence it seems not much is happening, however all bugs get fixed and currently no new features are planned. It is done.


var cc = require('coupon-code');

// generate a 3 part code
=> '55G2-DHM0-50NN'

// generate a 4 part code
cc.generate({ parts : 4 });
=> 'U5H9-HKDH-8RNX-1EX7'

// generate a code with partLen of 6
cc.generate({ partLen : 6 });
=> WYLKQM-U35V40-9N84DA

Now, when someone types their code in, you can check that it is valid. This means that letters like O are converted to 0 prior to checking.

// same code, just lowercased
=> '55G2-DHM0-50NN'

// various letters instead of numbers
=> '55G2-DHM0-50NN'

// wrong last character
=> ''

// not enough chars in the 2nd part
=> ''

// validate a code with 4 parts
cc.validate('U5H9-HKDH-8RNX-1EX7', { parts : 4 });
=> U5H9-HKDH-8RNX-1EX7

// validate a code with partLen of 6
cc.validate('WYLKQM-U35V40-9N84DA', { partLen : 6 });
=> WYLKQM-U35V40-9N84DA

The first thing we do to each code is uppercase it. Then we convert the following letters to numbers:

  • O -> 0
  • I -> 1
  • Z -> 2
  • S -> 5

This means [oizs], [OIZS] and [0125] are considered the same code.


Let's say you want a user to verify they got something, whether that is an email, letter, fax or carrier pigeon. To prove they received it, they have to type the code you sent them into a certain page on your website. You create a code which they have to type in:

var cc = require('coupon-code');

var code = cc.generate();
=> 55G2-DHM0-50NN

Time passes, letters get wet, carrier pigeons go on adventures and faxes are just as bad as they ever were. Now the user has to type their code into your website. The problem is, they can hardly read what the code was. Luckily we're somewhat forgiving since Z's and 2's are considered the same, O's and 0's, I's and 1's and S's and 5's are also mapped to each other. But even more than that, the 4th character of each group is a checkdigit which can determine if the other three in that group are correct. The user types this:


Because our codes are case insensitive and have good conversions for similar chars, the code is accepted as correct.

Also, since we have a checkdigit, we can use a client-side plugin to highlight to the user any mistake in their code before they submit it. Please see the original project (Algorithm::CouponCode) for more details of client side validation.


The easiest way to get it is via npm:

$ npm install coupon-code


To run the tests, use npm:

$ npm test


Inspired By

Grant McLean's Algorithm::CouponCode - with thanks. :)



See LICENSE for more details.