const {tap, of, map} = rxjs;

of(1, 2, 3, 4, 5)
  .pipe(
    tap((v) => document.body.insertAdjacentHTML('beforeend', `<div>Value before map: ${v}</div>`)),
    map((v) => v * v),
    tap((v) => document.body.insertAdjacentHTML('beforeend', `<div>Value after map: ${v}</div>`))
  )
  .subscribe((v) => console.log(v));