component-emitter

What is component-emitter?

The component-emitter package is a simple event emitter implementation that allows objects to subscribe to events, emit events, and remove event listeners. It is often used to add observer pattern capabilities to objects, enabling event-driven programming.

What are component-emitter's main functionalities?

Event subscription

This feature allows an object to listen for specific events using the 'on' method. When the event is emitted, the callback function is called.

const Emitter = require('component-emitter');
let emitter = new Emitter();
emitter.on('event', function(message) {
  console.log(message);
});

Event emission

This feature allows an object to emit an event, optionally passing arguments to the event listeners.

emitter.emit('event', 'Hello World!');

One-time event subscription

This feature allows an object to listen for an event only once. After the event is emitted and the listener is invoked, the listener is removed.

emitter.once('event', function(message) {
  console.log(message);
});

Event unsubscription

This feature allows an object to stop listening for specific events using the 'off' method.

function listener(message) {
  console.log(message);
}
emitter.on('event', listener);
emitter.off('event', listener);

Other packages similar to component-emitter

events

The 'events' package is Node.js's core EventEmitter class for managing and emitting events. It is similar to component-emitter but is built into Node.js and provides a more extensive API.

eventemitter3

EventEmitter3 is a high-performance event emitter. It offers a similar API to component-emitter but focuses on performance and is optimized for modern JavaScript engines.

wolfy87-eventemitter

Wolfy87's EventEmitter is an implementation of the EventEmitter module found in Node.js but can be used in the browser. It has additional features like namespacing events, but it's larger in size compared to component-emitter.

README

Emitter

Event emitter component.

Installation

$ component install component/emitter

API

Emitter(obj)

The Emitter may also be used as a mixin. For example a "plain" object may become an emitter, or you may extend an existing prototype.

As an Emitter instance:

var Emitter = require('emitter');
var emitter = new Emitter;
emitter.emit('something');

As a mixin:

var Emitter = require('emitter');
var user = { name: 'tobi' };
Emitter(user);

user.emit('im a user');

As a prototype mixin:

var Emitter = require('emitter');
Emitter(User.prototype);

Emitter#on(event, fn)

Register an event handler fn.

Emitter#once(event, fn)

Register a single-shot event handler fn, removed immediately after it is invoked the first time.

Emitter#off(event, fn)

• Pass event and fn to remove a listener.
• Pass event to remove all listeners on that event.
• Pass nothing to remove all listeners on all events.

Emitter#emit(event, ...)

Emit an event with variable option args.

Emitter#listeners(event)

Return an array of callbacks, or an empty array.

Emitter#hasListeners(event)

Check if this emitter has event handlers.

License

MIT