Where are intervals stored? - rxjs

Question

If I fire the following function 10 times
createInterval() {
var someInterval = interval(10000).pipe( take(1)).subscribe(
_intervalValue =>
{
console.log(" Interval Fired" + new Date().toISOString());
});
}
I get 10 intervals that will console log 10 times. How do I know that I have 10 intervals?
Where can I access these, it's like they exist mysteriously somewhere.

Answer 1

How do I know that I have 10 intervals?
Let's simplify using numbers instead of Observables:
function createNumber() {
const someNumber = Math.random();
console.log(`Number Created: ${someNumber}`);
}
for(let x=0; x<10; x++) {
createNumber();
}
And re-ask the same question: "How do I know that I have 10 numbers?"
Well... you don't. Not unless you're saving a reference to them!
So let's have the function return a reference to the number:
function createNumber() {
const someNumber = Math.random();
console.log(`Number Created: ${someNumber}`);
return someNumber;
}
let myNumbers = [];
for(let x=0; x<10; x++) {
myNumbers.push(createNumber());
}
console.log(`I know I have ${myNumbers.length} numbers!`);
This behavior is no different for observables. If you want know you have 10 intervals, you need to keep track of them:
function createInterval() {
return interval(1000)
.pipe(take(1))
.subscribe(
() => console.log(`Interval Fired: ${ new Date().toISOString() }`)
);
}
let mySubscriptions: Subscription[] = [];
for(let x=0; x<10; x++) {
mySubscriptions.push(createInterval());
}
mySubscriptions.forEach(
sub => sub.unsubscribe()
);
Note: by calling .subscribe() you are returning a Subscription, not an Observable. It is often convenient to have functions return the observable, and let consumers of the function call .subscribe():
function createInterval() {
return interval(1000).pipe(
take(1),
tap(() => console.log(`Interval Fired: ${ new Date().toISOString() }`))
);
}
let myObservables: Observable<number>[] = [];
for(let x=0; x<10; x++) {
myObservables.push(createInterval());
}
const mySubscriptions = myObservables.map(
obs => obs.subscribe()
);
// then later on, you can unsubscribe
mySubscriptions.forEach(
sub => sub.unsubscribe()
);