var source = Rx.Observable.interval(1000).take(3);

​

var observerA = {

    next: value => console.log('A next: ' + value),

    error: error => console.log('A error: ' + error),

    complete: () => console.log('A complete!')

}

​

var observerB = {

    next: value => console.log('B next: ' + value),

    error: error => console.log('B error: ' + error),

    complete: () => console.log('B complete!')

}

​

var subject = new Rx.Subject()

​

subject.subscribe(observerA)

​

source.subscribe(subject);

​

setTimeout(() => {

    subject.subscribe(observerB);

}, 1000);