import { } from "@effection-contrib/websocket"
WebSocket
Use the WebSocket
API as an Effection resource. Instead of a fragile, spring-loaded confederation
of 'open', 'close', 'error', and 'message' event handlers, useWebSocket()
organizes them for you so that you can consume all events from the server as a
plain stream that has state-readiness and proper error handling baked in.
To use a websocket import the useWebSocket()
operation which behaves just like
the WebSocket
constructor.
import { each, main } from "effection";
import { useWebSocket } from "@effection-contrib/websocket";
await main(function* () {
let socket = yield* useWebSocket("ws://websocket.example.org");
socket.send("Hello World");
for (let message of yield* each(socket)) {
console.log("Message from server", message);
yield* each.next();
}
});
The resource provides the following niceties:
- When
useWebSocket()
returns, it will have already received theopen
event. - If the socket recieves an error event, that event's error will be thrown to the current error boundary.
- The socket is a stream whose items are each
MessageEvents
, theCloseEvent
of the websocket will be the close event of that stream.
You can also instantiate a websocket separately and pass it along to
useWebSocket()
. This is helpful for runtimes such as NodeJS prior to version
21 that do not have built in support for websocket.
import { createWebSocket } from "my-websocket-client";
await main(function* () {
let socket = yield* useWebSocket(() =>
createWebSocket("ws://websocket.example.org")
);
for (let message of yield* each(socket)) {
console.log("Message from server", message);
yield* each.next();
}
});
API
interface WebSocketResource<T> extends Stream<MessageEvent<T>, CloseEvent> {
- binaryType: BinaryType;
the type of data that this websocket accepts
- bufferedAmmount: number;
- extensions: string;
- protocol: string;
- readyState: number;
- url: string;
- send(data: WebSocketData): void;
Handle to a
WebSocket
object
that can be consumed as an Effection stream. It has all the same properties as
the underlying WebSocket
apart from the event handlers. Instead, the resource
itself is a subscribale stream. When the socket is closed, the stream will
complete with a CloseEvent
A WebSocketResource does not have an explicit close method. Rather, the underlying socket will be automatically closed when the resource passes out of scope.
function useWebSocket(url: string, protocols?: string): Operation<WebSocketResource<T>>
Create a WebSocket resource using the native WebSocket constructor available on the current platform.
The resource will not be returned until a connection has been
succesffuly established with the server and the
open
has been received. Once initialized, it will crash if it receives
an error
event at any time.
Once created, the websocket resource can be use to consume events from the server:
let socket = yield* useWebSocket("ws://websocket.example.org");
for (let event of yield* each(socket)) {
console.log('event data: ', event.data);
yield* each.next();
}
function useWebSocket(create: () => WebSocket): Operation<WebSocketResource<T>>
Create a WebSocket
resource, but delegate the creation of the underlying websocket to a function
of your choice. This is necessary on platforms that do not have a global
WebSocket
constructor such as NodeJS <= 20.
The resource will not be returned until a connection has been
succesffuly established with the server and the
open
has been received. Once initialized, it will crash if it receives
an error
event at any time.
Once created, the websocket resource can be use to consume events from the server:
import * as ws from 'ws';
function* example() {
let socket = yield* useWebSocket(() => new ws.WebSocket("ws://websocket.example.org"));
for (let event of yield* each(socket)) {
console.log('event data: ', event.data);
yield* each.next();
}
}