RxJS - Sum numbers from 0 to 4 - Scan- Coding Blast - www.codingblast.com

rxjs-scan-numbers.ts

import {Observable} from 'rxjs';

console.time('timer');

let source = Observable
    .interval(100) // interval starts from 0
    .take(4)
    .scan((acc, val) => acc + val);

source.subscribe((value) => {
    console.timeEnd('timer');
    console.log('in next. Value: ', value);
});