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konami

A simple JavaScript module for adding Konami Code Easter Eggs

Konami Code JS module

@shgysk8zer0/konami

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The Konami Code (Japanese: コナミコマンド, Konami Komando, “Konami command”), also commonly referred to as the Contra Code and sometimes the 30 Lives code, is a cheat code that appears in many Konami video games, as well as some non-Konami games. In the original code, the player has to press the following sequence of buttons on the game controller to enable a cheat or other effects:

↑ ↑ ↓ ↓ ← → ← → B A; sometimes Start and/or Select is added to the sequence (usually to start Single player or, Two player modes). ~Konami Code | Wikipedia

About

konami.js enables developers to easily add the Konami Code to their websites. Like other JavaScript solutions, this one adds keyboard listeners and waits for the specifc sequence of keys to be pressed. Unlike other solutions, however, this one:

Installation

npm

npm i @shgysk8zer0/konami

Git Submodule

git submodule add https://github.com/shgysk8zer0/konami.git js/konami

CDN (unpkg)

const { konami } = await import('https://unpkg.com/@shgysk8zer0/konami');

Updating

Git Submodule

git submodule update --remote -- js/konami

Tip: Use Dependabot to automatically get Pull Requests when a submodule or package is updated.

Options

import { konami } from '/js/konami/konami.js';

await konami({ target, delay, signal, capture });
Name Type Default Value Description
target EventTarget globalThis Target to listen for input on
delay Number 1000 Allowed delay in ms between inputs
signal AbortSignal undefined See signal on MDN
capture Boolean true See capture on MDN

Example

From Submodule

import { konami } from '/js/konami/konami.js';

konami().then(/* Enter Cheat Mode! */);

From npm


import { konami } from '@shgysk8zer0/konami';
// or const { konami } = require('@shgysk8zer0/konami');

konami().then(/* Enter Cheat Mode! */);

Advanced

const controller = new AbortController();
// This will use version 1.0.5
const { konami } = await import('https://unpkg.com/@shgysk8zer0/konami@1.0.5/konami.js');

try {
  await konami({
    delay: 500,
    target: document.getElementById('konami-target'),
    signal: controller.signal,
    capture: true,
  });

  /* Enter Cheat Mode! */
} catch(err) {
  // Signal was aborted
}

Requirements

Due to use of signal, support is currently limited to browsers supporting AbortSignal & AbortController. Support may be extended to other browser by importing a polyfill.

Supported Browsers

Browser Supported Version Released
Internet Explorer 𐄂    
Edge 16 2017-10-16
Safari 12.1 2019-03-24
Chrome 66 2018-04-16
Firefox 57 2017-11-13
Node 15 ?
Deno 1.0 ?