coupon-code

An implementation of Perl's Algorithm::CouponCode for NodeJS.

npm install coupon-code
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An implementation of Perl's Algorithm::CouponCode for NodeJS. Thanks to Grant for the inspiration. :)

Synopsis

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

// generate a 3 part code
cc.generate();
=> '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
cc.validate('55g2-dhm0-50nn');
=> '55G2-DHM0-50NN'

// various letters instead of numbers
cc.validate('SSGZ-DHMO-SONN');
=> '55G2-DHM0-50NN'

// wrong last character
cc.validate('55G2-DHM0-50NK');
=> ''

// not enough chars in the 2nd part
cc.validate('55G2-DHM-50NN');
=> ''

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.

Example

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:

[s5g2-dhmo-50nn]

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.

Installation

The easiest way to get it is via npm:

$ npm install coupon-code

Tests

To run the tests, use npm:

$ npm test

Author

Inspired By

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

License

MIT.

See LICENSE for more details.

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