Ensuring Cleanup with Finally

We've already covered the try/catch part of try/catch/finally, so what about finally? We have the finally operator which calls a function after the source sequence terminates gracefully or exceptionally. This is useful if you are using external resources or need to free up a particular variable upon completion.

In this example, we can ensure that our WebSocket will indeed be closed once the last message is processed.

var socket = new WebSocket('ws://someurl', 'xmpp');

var source = Rx.Observable.from(data)
  .finally(() => socket.close());

var subscription = source.subscribe(
  data => {
    socket.send(data);
  }
);