Upon running the following code, you'll notice that an xhr request is being sent to the console regardless of whether I am subscribed to the subject or not. I would prefer for these requests not to be made if I am not subscribed.
// To start, install rxjs using npm
const Rx = require('rxjs/Rx');
let subject = new Rx.BehaviorSubject(null)
Rx.Observable.timer(0, 1000).subscribe(i => someApiCall(i));
// At this point, an xhr request will be sent every second
function someApiCall(i){
// Fetch some data
console.log("xhr request sent")
subject.next(i);
}
// Now we subscribe to the subject, making prior xhr requests useless
let subscription;
setTimeout(() => subscription = subject.subscribe(i => console.log(i)),2500);
setTimeout(() => subscription.unsubscribe(),6000);
// Despite unsubscribing, the xhr requests still continue
I opted for the behaviorSubject instead of directly subscribing to the observable because I need to instantly receive the last value from the previous xhr request when resubscribing.