websocket-ts

A client-websocket written in TypeScript to be used from within browsers with focus on simplicity, reliability and extensibility. It provides convenient features to automatically reconnect and buffer pending messages.

Features

• Dependency-free & small in size
• Uses the browser-native WebSocket-functionality
  • Copies the event-based WebSocket-API
  • Provides low-level access to the underlying WebSocket if needed
• Optional automatic reconnects
  • With easy-to-configure parameters (time between retries)
• Optional pending-messages
  • With easy-to-configure buffers (size, behaviour)
• Builder-class for easy initialization and configuration

Usage

New instances can be easily created through the Builder-class.

const ws = new Builder('ws://localhost:42421').build();

Callbacks

You can register callbacks for onOpen-, onClose-, onError- and onMessage-events. The callbacks get called with the websocket-instance that caused the event plus the event as parameters.

const ws = new Builder('ws://localhost:42421')
    .onOpen((i, e) => { console.log("opened") })
    .onClose((i, e) => { console.log("closed") })
    .onError((i, e) => { console.log("error") })
    .onMessage((i, e) => { i.send(e.data) })
    .build();

It is possible to register multiple callbacks for the same event, they are called in stack-order:

const ws = new Builder('ws://localhost:42421')
    .onMessage((i, e) => { console.log("sent echo") })
    .onMessage((i, e) => { i.send(e.data) })
    .onMessage((i, e) => { console.log("message received") })
    .build();

Buffer

To buffer pending messages while your websocket is disconnected, configure it to use a Buffer. These pending messages will be sent out as soon as the connection is (re)-established.

const ws = new Builder('ws://localhost:42421')
    .withBuffer(new LRUBuffer(100)) // buffers up to 100 messages, substitutes old messages with new ones
    .build();

const ws = new Builder('ws://localhost:42421')
    .withBuffer(new TimeBuffer(5 * 60 * 1000)) // buffers messages that were written within the last 5 minutes
    .build();

Reconnect / Backoff

To configure the websocket to automatically reconnect when the connection gets lost, provide it with a Backoff. The type of backoff provided decides the delay between connection-retries.

const ws  = new Builder('ws://localhost:42421')
    .withBackoff(new ConstantBackoff(500)) // Always waits 500 ms between retries
    .build();

const ws  = new Builder('ws://localhost:42421')
    .withBackoff(new ExponentialBackoff(100)) // Doubles the time between reconnects with every try
    .build();