import { timer, interval } from 'rxjs';
import { window, scan, mergeAll } from 'rxjs/operators';
//emit immediately then every 1s
const source = timer(0, 1000);
const example = source.pipe(window(interval(3000)));
const count = example.pipe(scan((acc, curr) => acc + 1, 0));
const subscribe = count.subscribe(val => console.log(`Window ${val}:`));
const subscribeTwo = example
.subscribe(val => console.log(val));