var source = Rx.Observable

    .fromArray([

        Rx.Notification.createOnNext(42),

        Rx.Notification.createOnCompleted()

    ])

    .dematerialize();

​

var subscription = source.subscribe(

  x => console.log(`onNext: ${x}`),

  e => console.log(`onError: ${e}`),

  () => console.log('onCompleted'));

​

// => onNext: 42

// => onCompleted

​