Konami

Konami is a Javascript plugin that allows for custom functions to be called when the user inputs the Konami Code using either the keyboard or touch-based input.

The Konami Code

Traditionally, the Konami Code consists of 10 key or button presses as originally used in Gradius for the Nintendo Entertainment System.

The sequence goes:

The last button is typically "START" because the code is frequently entered during a pause or start screen and the final "START" resumes or starts the game. For this reason, "START" ("Enter") is included in the default Konami Code in this plugin.

Usage

Include the following in the <head> of your document:

<script type="text/javascript" src="dist/konami.min.js"></script>

To initialize the plugin, add the following to your document:

<script type="text/javascript">
    const konami = new Konami();

    konami.init();
</script>

Whenever the correct code is entered, the plugin will trigger a custom event named konami.

Add an event listener to fire any time the code is entered:

document.addEventListener("konami", function () {
    alert("999 Lives!")
});

For best cross-browser performance, a custom event listener is included:

konami.listen(function () {
    alert("All Weapons!")
});

Building

Install and then build with yarn or npm:

yarn install
yarn run build

The library can be found at: dist/konami.js

Gestures

This plugin is also touchscreen gesture enabled. Swiping in the intended direction will be interpreted as that button press. For example, swiping up (bottom to top) will register as "UP".

Non-directional buttons (["A", "B", "START"]) will accept any gesture given. Typically, a simple tap will suffice.

Also, it is important to set up your mobile application to prevent default elastic scrolling behavior on iOS:

document.addEventListener('touchmove', function (e) {
    e.preventDefault();
}, false);

Source

Configuration

There are a number of configurable aspects of this plugin.

Trigger

By default, the custom event that is fired upon completion of the sequence is konami. This may be changed:

Konami.trigger = "konami_code";

Sequence

The default sequence included in this plugin is:

["UP", "UP", "DOWN", "DOWN", "LEFT", "RIGHT", "LEFT", "RIGHT", "B", "A", "START"]

"START" is aliased to the "Enter" key.

You may create your own sequences to use with this plugin. For example, if you wanted to leave off the final "START", this is how you would configure:

Konami.sequence = ["UP", "UP", "DOWN", "DOWN", "LEFT", "RIGHT", "LEFT", "RIGHT", "B", "A"]

Limit

The plugin can fire the konami event a custom amount of times.

Konami.limit = 1;

This will make the event fire only once. false (the default setting) will allow it to fire forever while 0 would prevent it from firing at all.

Debug

Activating the debugger for this plugin may be useful for diagnosing some touch-related problems when meshing with your application.

Konami.debug = true;

Turning the debugger on will console.log the button that has just been pressed. On older browsers, button presses will be alerted.

Tested Environments

Tested and working on:

Desktop

Google Chrome (Mac + PC)
Firefox (Mac + PC)
Safari (Mac + PC)
Opera (Mac + PC)
IE8, IE9

Mobile

Safari (iPhone)

kevinselwyn/konami