Eventment NPM | npm.io

Eventment

Node's event emitter for all engines with some extra features✨ With class

This implements the Node.js events module for environments that do not have it, like browsers.

events currently matches the Node.js API: Event: 'newListener' Event: 'removeListener' emitter.addListener(eventName, listener) emitter.emit(eventName, ...args) emitter.eventNames() emitter.getMaxListeners() emitter.listenerCount(eventName) emitter.listeners(eventName) emitter.off(eventName, listener) emitter.on(eventName, listener) emitter.once(eventName, listener) emitter.prependListener(eventName, listener) emitter.prependOnceListener(eventName, listener) emitter.removeAllListeners(eventName) emitter.removeListener(eventName, listener) emitter.setMaxListeners(n) emitter.rawListeners(eventName)

Install

npm i eventment

Usage

import Eventment from 'eventment';
const eventment = new Eventment();

eventment.on('message', event => {
  console.log('on message', event);
});

eventment.emit('message', { hello: 'world' });

API

See the Node.js EventEmitter docs. events currently matches the Node.js API.

Extra features ✨

Multiple arguments

Allows issuing multiple arguments to listeners and emitters in a simple usage.

eventment.on('message', (event1, event2) => {
  console.log('on message', { event1, event2 });
});

eventment.emit('message', { some: 'message' }, { my: 'event' });

Multiple events

It is possible to multiple events in a listener and contrary.

It works for: .on, .once, .attach, .collect, .enable, .disable

eventment.on([ 'message', 'letter' ], data => {
  console.log('on message or letter', data);
});

eventment.emit('message', { my: 'message' });
eventment.emit('letter', { my: 'letter' });

// Or also
eventment.on('message', data => {
  console.log('on message', data);
});
eventment.on('letter', data => {
  console.log('on letter', data);
});

eventment.emit([ 'message', 'letter' ], { my: 'message', or: 'letter' });

Promisify `.on` and `.once`

In case there is no callback, the on and once functions return events in promises.

let count = 0;
setInterval(() => eventment.emit('plus', count++), 500);

const number = await eventment.once('plus');
console.log('once promise', { number });

for await (const number of eventment.on('plus')){
  console.log('on promise', { number });
  if(number >= 10) break;
}

Functions `.attach` and `.collect`

Accumulate events and capture later.

eventment.attach('thing');

eventment.emit('thing', '💻');
eventment.emit('thing', '⌚');
eventment.emit('thing', '🕹️');

const things = eventment.collect('thing');
// [ '💻', '⌚', '🕹️' ]

// With filter
eventment.attach('thing', thing => [ '💻', '⌨️', '🖱️' ].includes(thing));

eventment.emit('thing', '💻');
eventment.emit('thing', '⌨️');
eventment.emit('thing', '🖱️');
eventment.emit('thing', '💻');
eventment.emit('thing', '⌚');
eventment.emit('thing', '🕹️');

const things = eventment.collect('thing');
// [ '💻', '⌨️', '🖱️', '💻' ]

Functions `.enable` and `.disable`

eventment.on('fruit', fruit => console.log('on fruit', fruit));

eventment.emit('fruit', '🍏'); // listener working
eventment.emit('fruit', '🍊'); // listener working

eventment.disable('fruit');
eventment.emit('fruit', '🍇'); // do nothing
eventment.emit('fruit', '🍓'); // do nothing

eventment.enable('fruit');
eventment.emit('fruit', '🥑'); // listener working
eventment.emit('fruit', '🍍'); // listener working

Chained callbacks

Allows listeners with chained callbacks.

eventment.on('divergence', (num1, num2) => {
  console.log('on divergence', { num1, num2 });
  return num1 * num2;
}, (product, num1, num2) => {
  console.log('on product', { product, num1, num2 });
  return Math.pow(product, 2);
}, (square, num1, num2) => {
  console.log('on square', { square, num1, num2 });
});

let count1 = 0, count2 = 0;
eventment.emit('divergence', count1++, count2--);

Global listener `*`

Listen to all events with *

eventment.on('*', (event, data) => {
  console.log('on event', event, data);
});

eventment.emit('message', { my: 'event' });
eventment.emit('signal', { my: 'signal' });

Bind listener

Bind emitter in callback

const messageEmitterCallback = eventment.bind('message');
messageEmitterCallback({ my: 'data' });

eventment.on('message', data => {
  console.log('on event message', data);
});