How do I use share() operator properly?

Question

I have stream that is triggered by next() method of Rx BehaviorSubject. How do I share the pipedData$ stream between subscribers?

I tried to use share operator here to avoid heavy recalculations inside the map operator but no luck - every subscriber produces recalculations.

here's stackblitz for this issue

Also is it possible to get number of subscribers from the source?

import { interval, BehaviorSubject } from 'rxjs';
import { take, map, tap, share, debounceTime } from 'rxjs/operators';

const data$ = new BehaviorSubject(null);

interval(1000).pipe(
  tap(x => console.log('emit:')),
  take(3)
).subscribe((x)=>{
  data$.next(x)
});

const pipedData$ = data$.pipe(
  debounceTime(30),
  share(),
  map(x => Math.random()),
);

console.log("--=-=-=-=--=-=----=-=-=-=-==-")
pipedData$.subscribe(x => console.log(x));
pipedData$.subscribe(x => console.log(x));
pipedData$.subscribe(x => console.log(x));

Answer 1

Looks like you need to move share below map to get the desired behaviour.