A WebSocket for browsers with auto-reconnect and message buffering written in TypeScript.

Features

• Lightweight & Standalone: No dependencies, 2.1 kB minified & gzipped.
• Browser-native: Utilizes WebSocket API, offers direct access.
• Smart Reconnect: Optional auto-reconnect and message buffering.
• Easy Setup: Optional builder class for quick initialization.
• Well-Tested: High test coverage, well-documented for extensibility.
• Module Support: Supports CommonJS, and ES6 modules.

Installation

Install websocket-ts with npm:

$ npm install websocket-ts 

Quickstart

This example shows how to use the package, complete with message buffering and automatic reconnection. The created websocket will echo back any received messages. It will buffer messages when disconnected and attempt to reconnect every 1 second.

import {
  ArrayQueue,
  ConstantBackoff,
  Websocket,
  WebsocketBuilder,
  WebsocketEvent,
} from "websocket-ts";

// Initialize WebSocket with buffering and 1s reconnection delay
const ws = new WebsocketBuilder("ws://localhost:8080")
  .withBuffer(new ArrayQueue())           // buffer messages when disconnected
  .withBackoff(new ConstantBackoff(1000)) // retry every 1s
  .build();

// Function to output & echo received messages
const echoOnMessage = (i: Websocket, ev: MessageEvent) => {
  console.log(`received message: ${ev.data}`);
  i.send(`echo: ${ev.data}`);
};

// Add event listeners
ws.addEventListener(WebsocketEvent.open, () => console.log("opened!"));
ws.addEventListener(WebsocketEvent.close, () => console.log("closed!"));
ws.addEventListener(WebsocketEvent.message, echoOnMessage);

Usage

This will demonstrate how to use websocket-ts in your project using the provided WebsocketBuild-class.

For a more detailed description of the API, please refer to the API Documentation.

Initialization

Create a new instance with the WebsocketBuilder:

const ws = new WebsocketBuilder("ws://localhost:42421").build();

Events

There are six events which can be subscribed to through with event listeners:

export enum WebsocketEvent {
  open = "open",          // Connection opened
  close = "close",        // Connection closed
  error = "error",        // Error-induced closure
  message = "message",    // Message received
  retry = "retry",        // Reconnect attempt
  reconnect = "reconnect" // Successful reconnect
}

Add Event Listeners

Event listeners receive the websocket instance (i) and the triggering event (ev) as arguments.

const ws = new WebsocketBuilder("ws://localhost:42421")
  .onOpen((i, ev) => console.log("opened"))
  .onClose((i, ev) => console.log("closed"))
  .onError((i, ev) => console.log("error"))
  .onMessage((i, ev) => console.log("message"))
  .onRetry((i, ev) => console.log("retry"))
  .onReconnect((i, ev) => console.log("reconnect"))
  .build();

Remove Event Listeners

To unregister a specific event listener, use removeEventListener:

let ws: Websocket
/* ... */
ws.removeEventListener(WebsocketEvent.open, openEventListener);

Send Message

Use the send method to send a message to the server:

let ws: Websocket;
/* ... */
ws.send("Hello World!");

Reconnect & Backoff (Optional)

If you'd like the websocket to automatically reconnect upon disconnection, you can optionally provide a Backoff strategy. This sets the delay between reconnection attempts. There are three built-in Backoff implementations, or you can create your own by implementing the Backoff interface. If no Backoff is provided, the websocket will not attempt to reconnect.

ConstantBackoff

The ConstantBackoff strategy enforces a fixed delay between each reconnection attempt. To set a constant 1-second wait time, use:

const ws = new WebsocketBuilder("ws://localhost:42421")
  .withBackoff(new ConstantBackoff(1000)) // 1000ms = 1s
  .build();

LinearBackoff

The LinearBackoff strategy increases the delay between reconnection attempts linearly, up to an optional maximum. For example, to start with a 0-second delay and increase by 10 second for each retry, capping at 60 seconds, use:

const ws = new WebsocketBuilder("ws://localhost:42421")
  .withBackoff(new LinearBackoff(0, 10000, 60000)) // 0ms, 10s, 20s, 30s, 40s, 50s, 60s
  .build();

ExponentialBackoff

The ExponentialBackoff strategy doubles the delay between each reconnection attempt, up to a specified maximum. This approach is inspired by the binary exponential backoff algorithm commonly used in networking. For example, to generate a backoff series like [1s, 2s, 4s, 8s], use:

const ws = new WebsocketBuilder("ws://localhost:42421")
  .withBackoff(new ExponentialBackoff(1000, 6)) // 1s, 2s, 4s, 8s, 16s, 32s, 64s
  .build();

Buffer (Optional)

To buffer outgoing messages when the websocket is disconnected, you can optionally specify a Queue. This queue will temporarily store your messages and send them in sequence when the websocket (re)connects. Two built-in Queue implementations are available, or you can create your own by implementing the Queue interface. If no queue is provided, messages won't be buffered.

RingQueue

The RingQueue is a fixed-capacity, first-in-first-out (FIFO) queue. When it reaches capacity, the oldest element is removed to accommodate new ones. Reading from the queue returns and removes the oldest element. For instance, to set up a RingQueue with a 100-element capacity, use:

const ws = new WebsocketBuilder("ws://localhost:42421")
  .withBuffer(new RingQueue(100))
  .build();

ArrayQueue

The ArrayQueue offers an unbounded capacity, functioning as a first-in-first-out (FIFO) queue. Reading from this queue returns and removes the oldest element. To use an ArrayQueue, use:

const ws = new WebsocketBuilder("ws://localhost:42421")
  .withBuffer(new ArrayQueue())
  .build();

Build & Tests

To compile the project, execute npm run build. The codebase includes unit tests for all components. To run these tests, use npm run test.