calculate-luhn-mod-n

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!Node.js Package

Calculates Luhn Mod N check values

Code based on
with minimal modifications.

Installing

``sh
npm install calculate-luhn-mod-n
`

API

$3

Parameter | Description
--- | ---
codePointFromCharacter | Function to obtain a code point from a character
characterFromCodePoint | Function to obtain a character from a code point
n | Number of valid characters
input | Input string

Using

The following example is based on the one found at

`javascript
const map = 'abcdef'; // Character to code-point map
const calculateLuhnModN = require('calculate-luhn-mod-n');

const checkCharacter = calculateLuhnModN(character => map.indexOf(character), codePoint => map[codePoint], map.length, 'abcdef'))

// checkCharacter === 'e'
`

The following example uses JavaScript native functions (parseInt and toString) to do the mapping based on radix/mod 36.

`javascript
const calculateLuhnModN = require('calculate-luhn-mod-n');

function appendLuhnMod36(input) {
const radix = 36;

return input + calculateLuhnModN(character => Number.parseInt(character, radix), codePoint => codePoint.toString(radix).toUpperCase(), radix, input);
}

const output = appendLuhnMod36('1134806PJFB000010013CD18');
// output === '1134806PJFB000010013CD18D'
`

The following example builds upon the previous one and demonstrates a possible way to do validation against an arbitrary regular expression before calculating the check character.

`javascript
const calculateLuhnModN = require('calculate-luhn-mod-n');

function appendLuhnMod36(input) {
const radix = 36;
const pattern = /^([A-Z]|\d){4}\d{3}([A-Z]|\d){15}\d{2}$/;

if (!pattern.test(input)) {
throw new Error('Invalid identifier format!');
}

return input + calculateLuhnModN(character => Number.parseInt(character, radix), codePoint => codePoint.toString(radix).toUpperCase(), radix, input);
}

const output = appendLuhnMod36('1134806PJFB000010013CD18');
// output === '1134806PJFB000010013CD18D'
``