let timeout = 1000;

/**
 * Create a custom observable that creates a XHR request and returns complete when the promise is fulfilled 
 */
let observable = Rx.Observable.create((o) => {
    dataService.fetch('test.json')
        .then((data) => {
            o.onNext(data);
            o.onCompleted();
        })
        .fail(o.onError);
});


/**
 * Call our observable immediately and then add an interval for the polled requests
 */
let source = observable
    .take(1)
    .merge(
        Rx.Observable
            .interval(timeout)
            .flatMapLatest(observable)
    )



/**
 * Return events from the observable.
 */
source.subscribe(
    (data) => console.log(data),
    (error) => console.log(error),
    () => console.log('done')
);