@smoovy/emitter

Installation

yarn add @smoovy/emitter

or

npm install --save @smoovy/emitter

The event emitter

Import the emitter as usual:

import { EventEmitter } from '@smoovy/emitter';

Usage

To use the event emitter you can either create a new instance directly or use it as a parent class.

const emitter = new EventEmitter();
// or
class UltraFancyEmitter extends EventEmitter {}

Emitting events

You have multiple options when it comes to the emission of events:

// Emit a single value
emitter.emit('eventName', 'A random string');

// Emit an other data type (object)
emitter.emit('eventName', { name: 'Mistadobalina' });

// Emit multiple events with different data types
emitter.emit({
  eventName1: 'Some data',
  eventName2: [ 1, 2, 3, 4 ]
});

Listening/Unlistening for events

Listening to events is pretty simple:

emitter.on('eventName', (data) => {
  // Handle your data
});

To unlisten you have two options:

const listener = (data) => {};
const unlisten = emitter.on('eventName', listener);

// Unlisten from callback or...
unlisten();

// Unlisten the old-fashioned way
emitter.off('eventName', listener);

When you have many listeners going wild in your application, you can use this litte helper function to stack those:

import { listenCompose } from '@smoovy/listener';

const unlisten = listenCompose(
  emitter.on('eventName1', () => {}),
  emitter.on('eventName2', () => {}),
  emitter.on('eventName3', () => {})
);

// Easily unsubcribe from all simultaneously
unlisten();

listenCompose simply merges all "unsubscribe callbacks" into one

Reflecting events

Reflect events to a different emitter. Muted events will not be reflects:

const reflectedEmitter = new Emitter();

// Reflect events to reflectedEmitter
emitter.reflectEvents(reflectedEmitter);

// Listen for events
reflectedEmitter.on('eventName1', (msg) => console.log(msg));

// Dispatch event in base emitter
emitter.emit('eventName1', 'reflected'); // Displays 'reflected'

// Remove reflected emitters
emitter.unreflectEvents();

License

See the LICENSE file for license rights and limitations (MIT).