WebSocketStream: WebSocketStream() constructor

url

A string representing the URL of the WebSocket server you want to connect to with this WebSocketStream instance. Allowed URL schemes are "ws", "wss", "http", and "https".

options Optional

An object that can contain the following properties:

protocols Optional

A single string or an array of strings representing the sub-protocol(s) that the client would like to use, for example "amqp" or "mqtt". Subprotocols may be selected from the IANA WebSocket Subprotocol Name Registry or may be custom names jointly understood by the client and the server. A single server can implement multiple WebSocket sub-protocols, and handle different types of interactions depending on the specified value. If it is omitted, an empty array is used by default. If protocols is included, the connection will only be established if the server reports that it has selected one of these sub-protocols.

signal Optional

An AbortSignal belonging to an AbortController that you want to use to close the WebSocket connection.

SyntaxError DOMException

Thrown if the URL scheme is not one of "ws", "wss", "http", or "https".

The most basic example takes the URL of a WebSocket server as an argument:

const wss = new WebSocketStream("wss://example.com/wss");

A more advanced example could also include an options object containing custom protocols and/or an AbortSignal:

const controller = new AbortController();
const queueWSS = new WebSocketStream("wss://example.com/queue", {
  protocols: ["amqp", "mqtt"],
  signal: controller.signal,
});

At a later time, AbortController.abort() can be called when required to close the connection:

controller.abort();

Alternatively, you can use the WebSocketStream.close() method to close a connection, however this is mainly needed if you wish to specify a custom code and/or reason for the server to report.

See Using WebSocketStream to write a client for a complete example with full explanation.

Not currently a part of any specification. See https://github.com/whatwg/websockets/pull/48 for standardization progress.

• WebSocketStream: integrating streams with the WebSocket API, developer.chrome.com (2020)