import { timer } from 'rxjs';
import { tap, mapTo, share } from 'rxjs/operators';
const source = timer(1000);
//log side effect, emit result
const example = source.pipe(
tap(() => console.log('***SIDE EFFECT***')),
***NOT SHARED, SIDE EFFECT WILL BE EXECUTED TWICE***
const subscribe = example.subscribe(val => console.log(val));
const subscribeTwo = example.subscribe(val => console.log(val));
//share observable among subscribers
const sharedExample = example.pipe(share());
***SHARED, SIDE EFFECT EXECUTED ONCE***
const subscribeThree = sharedExample.subscribe(val => console.log(val));
const subscribeFour = sharedExample.subscribe(val => console.log(val));