npm install gtin-manager
// or
yarn add gtin-manager

import Manager from 'gtin-manager'

const manager = new Manager('12345678')

manager.contingent === 10000 // true

manager.index(0) === '1234567800004'    // true
manager.index(9999) === '1234567899992' // true
manager.index(10000)                    // Error: Index out of bounds
manager.index(-1)                       // Error: Index out of bounds

manager.all === ['1234567800011', '1234567800028', ... 9998 more items] // true