event-pubsub

What is event-pubsub?

The event-pubsub package is a Node.js module that provides a simple interface for implementing the publish-subscribe pattern. This pattern allows for the creation of a decoupled system where publishers and subscribers can communicate through events without being directly connected.

What are event-pubsub's main functionalities?

Event Emission

This feature allows you to emit events with a specified name and pass data to the event listeners. In the code sample, an event listener is set up to listen for the 'sayHello' event and emit that event with a parameter.

const EventPubSub = require('event-pubsub');
const events = new EventPubSub();

// Event listener
events.on('sayHello', name => console.log(`Hello, ${name}!`));

// Emit event
events.emit('sayHello', 'World');

Event Listening

This feature allows you to listen for events by name. When the event is emitted, the callback function is called with any data passed to the event. In the code sample, an event listener is set up to listen for the 'dataReceived' event.

const EventPubSub = require('event-pubsub');
const events = new EventPubSub();

// Event listener
events.on('dataReceived', data => console.log(`Data: ${data}`));

Once Listeners

This feature allows you to set up event listeners that will only be triggered once. After the event is emitted and the listener is invoked, the listener is removed. In the code sample, an event listener is set up to listen for the 'initialize' event and will only be triggered once.

const EventPubSub = require('event-pubsub');
const events = new EventPubSub();

// Event listener that fires once
events.once('initialize', () => console.log('Initialization complete.'));

Removing Listeners

This feature allows you to remove specific event listeners. In the code sample, an event listener is added and then removed for the 'message' event.

const EventPubSub = require('event-pubsub');
const events = new EventPubSub();

function onMessage(content) {
  console.log(`Message: ${content}`);
}

// Add and remove an event listener
events.on('message', onMessage);
events.off('message', onMessage);

Other packages similar to event-pubsub

eventemitter3

eventemitter3 is a high performance EventEmitter. It provides similar functionality to event-pubsub but focuses on performance and is compatible with different module systems (CommonJS, AMD, and browser globals).

mitt

mitt is a tiny functional event emitter / pubsub. It offers a similar publish-subscribe pattern but with a smaller footprint, making it a good choice for front-end development and projects where size is a concern.

wolfy87-eventemitter

wolfy87-eventemitter is an EventEmitter implementation that provides asynchronous event emitting and namespaced events. It is more feature-rich compared to event-pubsub, offering additional functionality such as context binding and wildcard events.

README

Event PubSub

npm info :

GitHub info :

Super light and fast Extensible PubSub events and EventEmitters for Node and the browser with support for ES6 by default, and ES5 versions for older verions of node and older IE/Safari versions.

Easy for any developer level. No frills, just high speed events following the publisher subscriber pattern!

Pretty GitHub.io site

See NPM stats for event-pubsub

EXAMPLE FILES

1. Node Event PubSub Examples
2. Browser Event PubSub Examples

Node Install
npm i --save event-pubsub
By default the ES6 version will be used. you can use the es5 version for older versions of node by requiring event-pubsub/es5.js.

Browser Install
see browser examples above or below

<script src='path/to/event-pubsub-browser.js'></script>
<!-- OR ES5 for older browser support
    <script src='path/to/event-pubsub-browser-es5.js'></script>
-->

Methods

Method	Arguments	Description
subscribe	type (string), handler(function)	will bind the handler function to the the type event. Just like addEventListener in the browser
on	same as above	same as above
unSubscribe	type (string), handler(function or *)	will unbind the handler function from the the type event. If the handler is *, all handlers for the event type will be removed. Just like removeEventListener in the browser, but also can remove all event handlers for the type.
off	same as above	same as above
publish	type (string), ...data arguments	will call all handler functions bound to the event type and pass all ...data arguments to those handlers
emit	same as above	same as above
trigger	same as above	same as above

While publish, subscribe, and unSubscribe are the proper method names for the publisher/subscriber model, we have included on, off, and emit as well because these are the most common event method names, and shorter. We have also kept the trigger method as an alias for publish and emit for backwards compatability with earlier versions of event-pubsub.

The * type

The * type is a special event type that will be triggered by any publish or emit the handlers for these should expect the first argument to be the type and all arguments after to be data arguments.

Basic Examples

NOTE - the only difference between node and browser code is how the events variable is created

• node const events = new Events
• browser const events = new window.EventPubSub;

Node

const Events = new require('event-pubsub');
const events=new Events;

events.on(
    'hello',
    function(data){
        console.log('hello event recieved ', data);
        events.emit(
            'world',
            {
                type:'myObject',
                data:{
                    x:'YAY, Objects!'
                }
            }
        )
    }
);

events.on(
    'world',
    function(data){
        console.log('World event got',data);
        events.off('*','*');
        console.log('Removed all events');
    }
);

events.emit(
    'hello',
    'world'
);

Basic Chaining

events.on(
    'hello',
    someFunction
).on(
    'goodbye',
    anotherFunction
).emit(
    'hello',
    'world'
);

events.emit(
    'goodbye',
    'complexity'
).off(
    'hello',
    '*'
);

Browser

HTML

    <!DOCTYPE html>
    <html>
        <head>
            <title>PubSub Example</title>
            <script src='../../event-pubsub-browser.js'></script>
            <!-- OR ES5 for older browser support
                <script src='../../event-pubsub-browser-es5.js'></script>
            -->
            <script src='yourAmazingCode.js'></script>
        </head>
        <body>
            ...
        </body>
    </html>

Inside Your Amazing Code

var events = new window.EventPubSub();

events.on(
    'hello',
    function(data){
        console.log('hello event recieved ', data);
        events.emit(
            'world',
            {
                type:'myObject',
                data:{
                    x:'YAY, Objects!'
                }
            }
        )
    }
);

 events.emit(
     'hello',
     'world'
 );

 events.emit(
     'hello',
     'again','and again'
 );

Basic Event Emitter and/or Extending Event PubSub

const Events = require('event-pubsub');

class Book extends Events{
    constructor(){
        super();
        //now Book has .on, .off, and .emit

        this.words=[];
    }

    add(...words){
        this.words.push(...words);
        this.emit(
            'added',
            ...words
        );
    }

    read(){
        this.emit(
            'reading'
        );
        console.log(this.words.join(' '));
    }
}

const book=new Book;

book.on(
    'added',
    function(...words){
        console.log('words added : ',words);
        this.read();
    }
);

book.add(
    'once','upon','a','time','in','a','cubicle'
);

ES5 extention example

const Events = require('event-pubsub/es5.js');

function Book(){
    //extend happens below
    Object.assign(this,new Events);
    //now Book has .on, .off, and .emit

    this.words=[];
    this.add=add;
    this.erase=erase;
    this.read=read;

    function add(){
        arguments.slice=Array.prototype.slice;

        this.words=this.words.concat(
            arguments.slice()
        );
        this.emit(
            'added',
            arguments.slice()
        );
    }

    function read(){
        this.emit(
            'reading'
        );
        console.log(this.words.join(' '));
    }

    return this;
};

const book=new Book;

book.on(
    'added',
    function(...words){
        console.log('words added : ',words);
        this.read();
    }
);

book.add(
    'once','upon','a','time','in','a','cubicle'
);