JSFiddle - React, Tailwind, and code Playground

HTML

<script src="https://unpkg.com/@reactivex/rxjs@5.2.0/dist/global/Rx.js"></script>

JavaScript

var source = Rx.Observable.interval(300).take(5);

var example = source
              .groupBy(x => x % 2);
              
example.subscribe(console.log);

// GroupObservable { key: 0, ...}
// GroupObservable { key: 1, ...}