eventemitter3

Emitting events

This feature allows you to emit events with a specified name and pass arguments to the event listeners.

const EventEmitter = require('eventemitter3');
const emitter = new EventEmitter();
emitter.on('greet', function(message) {
  console.log(message);
});
emitter.emit('greet', 'Hello World!');

Listening to events

This feature allows you to add a listener for a specific type of event. The listener will be invoked when an event with that name is emitted.

const EventEmitter = require('eventemitter3');
const emitter = new EventEmitter();
emitter.on('greet', function(message) {
  console.log(message);
});

Removing event listeners

This feature allows you to remove a specific listener from an event so that it no longer gets called when the event is emitted.

const EventEmitter = require('eventemitter3');
const emitter = new EventEmitter();
function onGreet(message) {
  console.log(message);
}
emitter.on('greet', onGreet);
emitter.removeListener('greet', onGreet);

Once listeners

This feature allows you to add a one-time listener for an event. The listener will be invoked only the first time the event is emitted, after which it is removed.

const EventEmitter = require('eventemitter3');
const emitter = new EventEmitter();
emitter.once('greet', function(message) {
  console.log('This will only be logged once:', message);
});
emitter.emit('greet', 'Hello World!');
emitter.emit('greet', 'Hello again!');