publish-selector.ts

import { concat, of, race, timer } from "rxjs";
import { delay, mapTo, publish } from "rxjs/operators";

const source = of(42).pipe(delay(100));
const composed = source.pipe(
  publish(published => race(
    published,
    concat(timer(10).pipe(mapTo(54)), published)
  ))
);
composed.subscribe(value => console.log(value));