RxJS ≥6 version

medium-rxjs-publish-mental-model.ts

import { defer, Observable, of, Subject } from "rxjs";

const source = defer(() => of(
  Math.floor(Math.random() * 100)
));

function observer(name: string) {
  return {
    next: (value: number) => console.log(`observer ${name}: ${value}`),
    complete: () => console.log(`observer ${name}: complete`)
  };
}

const subject = new Subject<number>();
subject.subscribe(observer("a"));
subject.subscribe(observer("b"));
source.subscribe(subject);