WebSocketSubjectConfig is a plain Object that allows us to make our webSocket configurable.

interface WebSocketSubjectConfig<T> {
  url: string
  protocol?: string | Array<string>
  resultSelector?: (e: MessageEvent) => T
  serializer?: (value: T) => WebSocketMessage
  deserializer?: (e: MessageEvent) => T
  openObserver?: NextObserver<Event>
  closeObserver?: NextObserver<CloseEvent>
  closingObserver?: NextObserver<void>
  WebSocketCtor?: {...}
  binaryType?: 'blob' | 'arraybuffer'
}

Description

Provides flexibility to webSocket

It defines a set of properties to provide custom behavior in specific moments of the socket's lifecycle. When the connection opens we can use openObserver, when the connection is closed closeObserver, if we are interested in listening for data comming from server: deserializer, which allows us to customize the deserialization strategy of data before passing it to the socket client. By default deserializer is going to apply JSON.parse to each message comming from the Server.

Example

deserializer, the default for this property is JSON.parse but since there are just two options for incomming data, either be text or binarydata. We can apply a custom deserialization strategy or just simply skip the default behaviour.

import { webSocket } from 'rxjs/webSocket';

const wsSubject = webSocket({
    url: 'ws://localhost:8081',
//Apply any transformation of your choice.
    deserializer: ({data}) => data
});

wsSubject.subscribe(console.log);

// Let's suppose we have this on the Server: ws.send("This is a msg from the server")
//output
//
// This is a msg from the server

serializer allows us tom apply custom serialization strategy but for the outgoing messages

import { webSocket } from 'rxjs/webSocket';

const wsSubject = webSocket({
    url: 'ws://localhost:8081',
//Apply any transformation of your choice.
    serializer: msg => JSON.stringify({channel: "webDevelopment", msg: msg})
});

wsSubject.subscribe(() => subject.next("msg to the server"));

// Let's suppose we have this on the Server: ws.send("This is a msg from the server")
//output
//
// {"channel":"webDevelopment","msg":"msg to the server"}

closeObserver allows us to set a custom error when an error raise up.

import { webSocket } from 'rxjs/webSocket';

const wsSubject = webSocket({
    url: 'ws://localhost:8081',
    closeObserver: {
        next(closeEvent) {
            const customError = { code: 6666, reason: "Custom evil reason" }
            console.log(`code: ${customError.code}, reason: ${customError.reason}`);
        }
    }
});

//output
// code: 6666, reason: Custom evil reason

openObserver, Let's say we need to make some kind of init task before sending/receiving msgs to the webSocket or sending notification that the connection was successful, this is when openObserver is usefull for.

import { webSocket } from 'rxjs/webSocket';

const wsSubject = webSocket({
    url: 'ws://localhost:8081',
    openObserver: {
        next: () => {
            console.log('connetion ok');
        }
    },
});

//output
// connetion ok`

Properties

Property	Type	Description
url	string	The url of the socket server to connect to
protocol	string | Array<string>	The protocol to use to connect
resultSelector	(e: MessageEvent) => T
serializer	(value: T) => WebSocketMessage	A serializer used to create messages from passed values before the messages are sent to the server. Defaults to JSON.stringify.
deserializer	(e: MessageEvent) => T	A deserializer used for messages arriving on the socket from the server. Defaults to JSON.parse.
openObserver	NextObserver<Event>	An Observer that watches when open events occur on the underlying web socket.
closeObserver	NextObserver<CloseEvent>	An Observer than watches when close events occur on the underlying webSocket
closingObserver	NextObserver<void>	An Observer that watches when a close is about to occur due to unsubscription.
WebSocketCtor	{ new (url: string, protocols?: string | string[]): WebSocket; }	A WebSocket constructor to use. This is useful for situations like using a WebSocket impl in Node (WebSocket is a DOM API), or for mocking a WebSocket for testing purposes
binaryType	'blob' | 'arraybuffer'	Sets the binaryType property of the underlying WebSocket.