initialize.md

Initialize

Like tap, but performs some side-effect immediately after subscribing.

export function initialize<T>(effect: () => void): MonoTypeOperatorFunction<T> {
  return s => new Observable(ob => {
    const sub = s.subscribe(ob);
    effect();
    return sub;
  });
}

Example:

const a$ = new Subject<number>();

a$.pipe(
 initialize(() => a$.next(5)),
 map(v => v + 1)
).subscribe(console.log);