How to use the botframework-directlinejs.ConnectionStatus.Online function in botframework-directlinejs

.subscribe((connectionStatus) => {
        this.conectionStatus = connectionStatus;
        switch (connectionStatus) {
          case ConnectionStatus.Uninitialized:
            // the status when the DirectLine object is first created/constructed
            break;
          case ConnectionStatus.Connecting:
            // currently trying to connect to the conversation
            if (program.verbose) {
              console.log('Connecting to DirectLine...');
            }
            break;
          case ConnectionStatus.Online:
            // successfully connected to the converstaion. Connection is healthy so far as we know.
            if (program.verbose) {
              console.log('Connected to DirectLine.');
            }
            if (this.onReadyCb) {
              this.onReadyCb();
            }
            break;
          case ConnectionStatus.ExpiredToken:
            // last operation errored out with an expired token. Your app should supply a new one.
            console.log('DirectLine error: token expired.');
            process.exit(1);
            break;
          case ConnectionStatus.FailedToConnect:
            // the initial attempt to connect to the conversation failed. No recovery possible.
            console.log('DirectLine error: failed to connect.');

connectionStatus$: new Observable(observer => {
                observer.next(ConnectionStatus.Uninitialized);
                observer.next(ConnectionStatus.Connecting);
                observer.next(ConnectionStatus.Online);
            }),
            activity$: new Observable(observer => {