KeyBus

:snowboarder: Support simultaneous multi-keypress handler. Especially useful in canvas game development on web browser. Also the standalone keyboard I/O component in the canvas game engine Zion.

Installation

npm install --save keybus

Basics Handler

The basic key handler serves exactly like what the browser native API supports:

import createKeyBus from 'keybus';
// pass in the dom element that you want the event handlers be bind to
const kb = createKeyBus(document);

const enterKeydownHandler = kb.down(13, () => console.log('Enter keydown!'));

// to remove the keydown event handler for a specific key and event
enterKeydownHandler.remove();

APIs:

Advanced Multi-key Handler

This is what the KeyBus is built for. Let's talk about the current situation of keypress handler first.

The native api addEventListener doesn't sufficiently support simultaneous keydown event (See more at https://stackoverflow.com/questions/15661796/how-to-handle-multiple-keypresses-with-canvas). If you have a moving character, which you could control its movement using wasd, the keyboard handlers will break down if you press w and d and want it to move top right simultaneously.

The stackoverflow post above shows a way to solve this problem, by using a hash table. But you still have to check the hash table every time you execute game_loop, which is a redundant concern to the developer. It's not a good way of abstraction.

However, with KeyBus, you could do this:

const canvas = document.getElementById('my-canvas')
const kb = createKeyBus(canvas)

kb.simulDown(38, () => console.log('up'))
kb.simulDown(39, () => console.log('right'))

function game_loop() {
  // the only thing you need to do is to call this method in every game loop,
  // the keybus will automatically check if anykey is pressed and run the according handlers (could be more than one)
  kb.executeMultiKeyHandlers();
}

Admittedly, under the hood there is still a hashtable. But as a consumer / developer, you are not aware of it, which ease most of the pain when handling this issue.