publisher-subscriber-pattern

About

• Javascript implementation of publisher subscriber pattern
• Can be used with various event emitters including browser's window object
• Provides Publisher class

Installation

npm i publisher-subscriber-pattern

Example

The example uses the browser's window object as emitterInstance. Other valid emitter instances can be also used.

import { Publisher } from 'publisher-subscriber-pattern';

const publisher = new Publisher(window, 'addEventListener','removeEventListener');

Publisher's subscribe method returns function, which can be used later to unsubscribe from the publisher's event.

const unsubscribe = publisher.subscribe('scroll', (event) => {});

// ...foo code...

unsubscribe();

There is also a method unsubscribeAll for unsubscribing all subscribers from all emitter's events.

publisher.unsubscribeAll();

API

Publisher

• Parameters: emitterInstance, addListenerMethodName, removeListenerMethodName
• Methods: subscribe, unsubscribeAll, eventSubscribersCount, subscribersCount

Parameters

emitterInstance

• Object, which exposes addListener and removeListener methods
• Behind the scenes, the emitterInstance is bound to addListener and removeListener methods as this (see Function.prototype.bind)

addListenerMethodName, removeListenerMethodName

• Names of methods (strings), which are exposed by emitterInstance and, which add and remove event listeners, respectively

Methods

subscribe

• Required parameters: eventName, eventCallback

• Optional parameter: subscriberInstance, which will be bound to the eventCallback argument as this (see Function.prototype.bind)

• Method subscribes eventCallback to eventName, so whenever event occurs the eventCallback is called

• Returns function for unsubscribing from the event

unsubscribeAll

• Unsubscribes all publisher's eventCallbacks from all emitter's eventNames

eventSubscriberCount

• Required parameter: eventName
• Returns number of subscribers' eventCallbacks subscribed to publisher's eventName

subscribersCount

• Returns number of subscriber's eventCallbacks subscribed to all publisher's eventNames

Dependencies

Production dependencies

• Package has no production dependencies

Main development dependencies

• Typescript
• Jasmine, chai, sinon
• Babel
• Node (EventEmitter)