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 = {

    observers: [],

    addObserver: function(observer) {

        this.observers.push(observer)

    },

    next: function(value) {

        this.observers.forEach(o => o.next(value))    

    },

    error: function(error){

        this.observers.forEach(o => o.error(error))

    },

    complete: function() {

        this.observers.forEach(o => o.complete())

    }

}

​

subject.addObserver(observerA)

​

source.subscribe(subject);

​

setTimeout(() => {

    subject.addObserver(observerB);

}, 1000);