pusher-js

What is pusher-js?

The pusher-js npm package is a JavaScript library for integrating real-time functionality into web and mobile applications. It allows developers to subscribe to channels and bind to events to receive real-time updates, making it ideal for applications that require live data feeds, notifications, and interactive features.

What are pusher-js's main functionalities?

Real-time Event Subscription

This feature allows you to subscribe to a channel and bind to specific events to receive real-time updates. The code sample demonstrates how to initialize Pusher, subscribe to a channel, and bind to an event to log received data.

const Pusher = require('pusher-js');
const pusher = new Pusher('YOUR_APP_KEY', {
  cluster: 'YOUR_APP_CLUSTER'
});
const channel = pusher.subscribe('my-channel');
channel.bind('my-event', function(data) {
  console.log('Received data:', data);
});

Presence Channels

Presence channels build on the functionality of public channels by allowing you to keep track of who is subscribed to the channel. The code sample shows how to subscribe to a presence channel and bind to events for when members are added or removed.

const Pusher = require('pusher-js');
const pusher = new Pusher('YOUR_APP_KEY', {
  cluster: 'YOUR_APP_CLUSTER'
});
const presenceChannel = pusher.subscribe('presence-my-channel');
presenceChannel.bind('pusher:subscription_succeeded', function(members) {
  console.log('Members:', members);
});
presenceChannel.bind('pusher:member_added', function(member) {
  console.log('Member added:', member);
});
presenceChannel.bind('pusher:member_removed', function(member) {
  console.log('Member removed:', member);
});

Private Channels

Private channels provide an extra layer of security by requiring authentication before subscribing. The code sample demonstrates how to subscribe to a private channel and bind to an event to log received data.

const Pusher = require('pusher-js');
const pusher = new Pusher('YOUR_APP_KEY', {
  cluster: 'YOUR_APP_CLUSTER',
  authEndpoint: '/pusher/auth'
});
const privateChannel = pusher.subscribe('private-my-channel');
privateChannel.bind('my-event', function(data) {
  console.log('Received data:', data);
});

Other packages similar to pusher-js

socket.io

Socket.IO is a popular library for real-time web applications. It enables real-time, bidirectional, and event-based communication between web clients and servers. Unlike pusher-js, which is a hosted service, Socket.IO can be self-hosted, giving developers more control over their infrastructure.

ably

Ably is a real-time messaging service that offers pub/sub messaging, presence, and push notifications. It provides similar functionalities to pusher-js but also includes additional features like message history and token-based authentication. Ably is known for its reliability and extensive feature set.

pubnub

PubNub is a real-time communication platform that offers a wide range of features including pub/sub messaging, presence, and mobile push notifications. It is similar to pusher-js in terms of real-time capabilities but also provides additional features like data stream storage and serverless functions.

README

Pusher Javascript Client

This library is an open source client that allows Javascript web browser clients to connect to the Pusher WebSocket API. It also supports fallback to HTTP connection transports. It is highly recommended that you use the hosted version of this file to stay up to date with the latest updates.

We have included the source code for following libraries:

• sockjs-client

They both include their own licences.

Usage overview

The following topics are covered:

• Supported runtimes and installation
  • Web
  • React Native
  • Web Workers
  • NodeJS
• Configuration
• Global configuration
• Connection
• Socket ids
• Subscribing to channels (public and private)
• Binding to events
  • Globally
  • Per-channel
• Default events

Installation

Web

If you're using PusherJS on a web page, you can install the library via:

CDN

<script src="//js.pusher.com/3.1/pusher.min.js"></script>

Bower

Or via Bower:

bower install pusher

and then

<script src="bower_components/pusher/dist/web/pusher.min.js"></script>

NPM

npm install pusher-js

Then simply call:

var Pusher = require('pusher-js');

React Native

You can install pusher-js from NPM, then import the react-native path of PusherJS.

import Pusher from 'pusher-js/react-native';

Notes:

• The fallbacks available for this runtime are HTTP streaming and polling.
• This build uses React Native's NetInfo API to detect changes on connectivity state. It will use this to automatically reconnect.

Web Workers

You can import the worker script (pusher.worker.js, not pusher.js) from the CDN:

importScripts("https://js.pusher.com/3.1/pusher.worker.min.js");

Notes:

• For standard WebWorkers, this build will use HTTP as a fallback.
• For ServiceWorkers, as the XMLHttpRequest API is unavailable, there is currently no support for HTTP fallbacks. However, we are open to requests for fallbacks using fetch if there is demand.

Initialization

var pusher = new Pusher(APP_KEY);

Configuration

There are a number of configuration parameters which can be set for the Pusher client, which can be passed as an object to the Pusher constructor, i.e.:

var pusher = new Pusher(APP_KEY, {
    authEndpoint: "http://example.com/pusher/auth",
    encrypted: true
});

For most users, there is little need to change these. See client API guide for more details.

encrypted (Boolean)

Forces the connection to use encrypted transports.

authEndpoint (String)

Endpoint on your server that will return the authentication signature needed for private channels.

authTransport (String)

Defines how the authentication endpoint, defined using authEndpoint, will be called. There are two options available: ajax and jsonp.

auth (Hash)

Allows passing additional data to authorizers. Supports query string params and headers (AJAX only). For example, following will pass foo=bar via the query string and baz: boo via headers:

var pusher = new Pusher(API_KEY, {
  auth: {
    params: { foo: "bar" },
    headers: { baz: "boo" }
  }
});

CSRF

If you require a CSRF header for incoming requests to the private channel authentication endpoint on your server, you should add a CSRF token to the auth hash under headers. This is applicable to frameworks which apply CSRF protection by default.

var pusher = new Pusher(API_KEY, {
  auth: {
    params: { foo: "bar" },
    headers: { "X-CSRF-Token": "SOME_CSRF_TOKEN" }
  }
});

cluster (String)

Allows connecting to a different datacenter by setting up correct hostnames and ports for the connection.

// will connect to the 'eu' cluster
var pusher = new Pusher(API_KEY, { cluster: "eu" });

disableStats (Boolean)

Disables stats collection, so that connection metrics are not submitted to Pusher’s servers.

enabledTransports (Array)

Specifies which transports should be used by Pusher to establish a connection. Useful for applications running in controlled, well-behaving environments. Available transports for web: ws, wss, xhr_streaming, xhr_polling, sockjs. Additional transports may be added in the future and without adding them to this list, they will be disabled.

// will only use WebSockets
var pusher = new Pusher(API_KEY, { enabledTransports: ["ws"] });

disabledTransports (Array)

Specified which transports must not be used by Pusher to establish a connection. This settings overwrites transports whitelisted via the enabledTransports options. Available transports for web: ws, wss, xhr_streaming, xhr_polling, sockjs. Additional transports may be added in the future and without adding them to this list, they will be enabled.

// will use all transports except for sockjs
var pusher = new Pusher(API_KEY, { disabledTransports: ["sockjs"] });

// will only use WebSockets
var pusher = new Pusher(API_KEY, {
  enabledTransports: ["ws", "xhr_streaming"],
  disabledTransports: ["xhr_streaming"]
});

wsHost, wsPort, wssPort, httpHost, httpPort, httpsPort

These can be changed to point to alternative Pusher URLs (used internally for our staging server).

ignoreNullOrigin (Boolean)

Ignores null origin checks for HTTP fallbacks. Use with care, it should be disabled only if necessary (i.e. PhoneGap).

activityTimeout (Integer)

After this time (in miliseconds) without any messages received from the server, a ping message will be sent to check if the connection is still working. Default value is is supplied by the server, low values will result in unnecessary traffic.

pongTimeout (Integer)

Time before the connection is terminated after sending a ping message. Default is 30000 (30s). Low values will cause false disconnections, if latency is high.

Global configuration

Pusher.logToConsole (Boolean)

Enables logging to the browser console via calls to console.log.

Pusher.log (Function)

Assign a custom log handler for the Pusher library logging. For example:

Pusher.log = function(msg) {
  console.log(msg);
};

By setting the log property you also override the use of Pusher.enableLogging.

Connection

A connection to Pusher is established by providing your API key to the constructor function:

var socket = new Pusher(API_KEY);

This returns a socket object which can then be used to subscribe to channels.

Socket IDs

Making a connection provides the client with a new socket_id that is assigned by the server. This can be used to distinguish the client's own events. A change of state might otherwise be duplicated in the client. More information on this pattern is available here.

It is also stored within the socket, and used as a token for generating signatures for private channels.

Subscribing to channels

Public channels

The default method for subscribing to a channel involves invoking the subscribe method of your socket object:

var my_channel = socket.subscribe('my-channel');

This returns a Channel object which events can be bound to.

Private channels

Private channels are created in exactly the same way as normal channels, except that they reside in the 'private-' namespace. This means prefixing the channel name:

var my_channel = socket.subscribe('private-my-channel');

It is possible to access channels by name, through the channel function:

channel = socket.channel('private-my-channel');

It is possible to access all subscribed channels through the allChannels function:

var channels = socket.allChannels();
console.group('Pusher - subscribed to:');
for (var i = 0; i < channels.length; i++) {
    var channel = channels[i];
    console.log(channel.name);
}

console.groupEnd();

Private and presence channels will make a request to your authEndpoint (/pusher/auth) by default, where you will have to authenticate the subscription. You will have to send back the correct auth response and a 200 status code.

Unsubscribing from channels

To unsubscribe from a channel, invoke the unsubscribe method of your socket object:

socket.unsubscribe('my-channel');

Unsubscribing from private channels is done in exactly the same way, just with the additional private- prefix:

socket.unsubscribe('private-my-channel');

Binding to events

Events can be bound to at 2 levels, the global, and per channel. They take a very similar form to the way events are handled in jQuery.

Global events

You can attach behaviour to these events regardless of the channel the event is broadcast to. The following is an example of an app that binds to new comments from any channel:

var socket = new Pusher('MY_API_KEY');
var my_channel = socket.subscribe('my-channel');
socket.bind('new-comment',
  function(data) {
    // add comment into page
  }
);

Per-channel events

These are bound to a specific channel, and mean that you can reuse event names in different parts of your client application. The following might be an example of a stock tracking app where several channels are opened for different companies:

var socket = new Pusher('MY_API_KEY');
var channel = socket.subscribe('APPL');
channel.bind('new-price',
  function(data) {
    // add new price into the APPL widget
  }
);

Bind event handler with optional context

It is possible to provide a third, optional parameter that is used as the this value when calling a handler:

var context = { title: 'Pusher' };
var handler = function(){
  console.log('My name is ' + this.title);
};
channel.bind('new-comment', handler, context);

Unbind event handlers

Remove previously-bound handlers from an object. Only handlers that match all of the provided arguments (eventName, handler or context) are removed:

channel.unbind('new-comment', handler); // removes just `handler` for the `new-comment` event
channel.unbind('new-comment'); // removes all handlers for the `new-comment` event
channel.unbind(null, handler); // removes `handler` for all events
channel.unbind(null, null, context); // removes all handlers for `context`
channel.unbind(); // removes all handlers on `channel`

Binding to everything

It is possible to bind to all events at either the global or channel level by using the method bind_all. This is used for debugging, but may have other utilities.

Batching auth requests (aka multi-auth)

Currently, pusher-js itself does not support authenticating multiple channels in one HTTP request. However, thanks to @dirkbonhomme you can use the pusher-js-auth plugin that buffers subscription requests and sends auth requests to your endpoint in batches.

Default events

There are a number of events which are used internally, but can also be of use elsewhere:

• connection_established
• subscribe

Self-serving JS files

You can host JavaScript files yourself, but it's a bit more complicated than putting them somewhere and just linking pusher.js in the source of your website. Because pusher-js loads fallback files dynamically, the dependency loader must be configured correctly or it will be using js.pusher.com.

First, clone this repository and run npm install && git submodule init && git submodule update. Then run:

$ CDN_HTTP='http://your.http.url' CDN_HTTPS='https://your.https.url' make web

In the dist/web folder, you should see the files you need: pusher.js, pusher.min.js, json2.js, json.min.js, sockjs.js and sockjs.min.js. pusher.js should be built referencing your URLs as the dependency hosts.

First, make sure you expose all files from the dist directory. They need to be in a directory with named after the version number. For example, if you're hosting version 3.1.0 under http://example.com/pusher-js (and https for SSL), files should be accessible under following URL's:

http://example.com/pusher-js/3.1.0/pusher.js
http://example.com/pusher-js/3.1.0/json2.js
http://example.com/pusher-js/3.1.0/sockjs.js

Minified files should have .min in their names, as in the dist/web directory:

http://example.com/pusher-js/2.1.3/pusher.min.js
http://example.com/pusher-js/2.1.3/json2.min.js
http://example.com/pusher-js/2.1.3/sockjs.min.js

SockJS compatibility

Most browsers have a limit of 6 simultaneous connections to a single domain, but Internet Explorer 6 and 7 have a limit of just 2. This means that you can only use a single Pusher connection in these browsers, because SockJS requires an HTTP connection for incoming data and another one for sending. Opening the second connection will break the first one as the client won't be able to respond to ping messages and get disconnected eventually.

All other browsers work fine with two or three connections.

Developing

Install all dependencies via NPM:

npm install

Run a development server which serves bundled javascript from http://localhost:5555/pusher.js so that you can edit files in /src freely.

make serve

You can optionally pass a PORT environment variable to run the server on a different port. You can also pass CDN_HTTP and CDN_HTTPS variables if you wish the library to load dependencies from a new host.

This command will serve pusher.js, sockjs.js, json2.js, and their respective minified versions.

Core Vs. Platform-Specific Code

New to PusherJS 3.1 is the ability for the library to produce builds for different runtimes: classic web, React Native, NodeJS and Web Workers.

In order for this to happen, we have split the library into two directories: core/ and runtimes/. In core we keep anything that is platform-independent. In runtimes we keep code that depends on certain runtimes.

Throughout the core/ directory you'll find this line:

import Runtime from "runtime";

We use webpack module resolution to make the library look for different versions of this module depending on the build.

For web it will look for src/runtimes/web/runtime.ts. For ReactNative, src/runtimes/react-native/runtime.ts. For Node: src/runtimes/node/runtime.ts. For worker: src/runtimes/worker/runtime.ts.

Each of these runtime files exports an object (conforming to the interface you can see in src/runtimes/interface.ts) that abstracts away everything platform-specific. The core library pulls this object in without any knowledge of how it implements it. This means web build can use the DOM underneath, the ReactNative build can use its native NetInfo API, Workers can use fetch and so on.

Building

In order to build SockJS, you must first initialize and update the Git submodule:

git submodule init
git submodule update

Then simply run:

make web

This will build the source files relevant for the web build into dist/web.

In order to specify the library version, you can either update package.json or pass a VERSION environment variable upon building.

Other build commands include:

make react-native # for the React Native build
make node         # for the NodeJS build
make worker       # for the worker build

Testing

Each test environment contains two types of tests:

1. unit tests,
2. integration tests.

Unit tests are simple, fast and don't need any external dependencies. Integration tests usually connect to production and js-integration-api servers and can use a local server for loading JS files, so they need an Internet connection to work.

There are 3 different testing environments: one for web, one for NodeJS and one for workers. We may consider adding another one for React Native in the future.

The web and worker tests use Karma to execute specs in real browsers. The NodeJS tests use jasmine-node.

To run the tests:

# For web
make web_unit
make web_integration

# For NodeJS
make node_unit
make node_integration

# For workers
make worker_unit
make worker_integration

If you want your Karma tests to automatically reload, then in spec/karma/config.common.js set singleRun to false.