RxJS fiddles

clickToAdvance.js

const { of, fromEvent } = Rx;
const { expand, map, zip } = RxOperators;

const click$ = fromEvent(document, 'click')

of(1).pipe(
  expand(x => (
    of(x + 1)
      .pipe(
        zip(click$),
        map(([x]) => x)
      )
  ))
)

mergeScan.js

const { fromEvent, of, from } = Rx;
const { merge, mapTo, scan, mergeScan, mergeMap, delay, first } = RxOperators;

const button = document.createElement('button')
button.innerText = 'Step'
output.prepend(button)

fromEvent(button, 'click').pipe(
  mapTo(1),
  mergeScan((x, y) => 
    from([-1, 1]).pipe(
      mergeMap(d => of(x + d).pipe(delay(Math.random() * 50))), first()
  ), 0)
)

multipleOperations.js

const { of, from, fromEvent, Observable } = Rx;
const { expand, delay, map, zip, mergeMap, first } = RxOperators;

const click$ = fromEvent(document, 'click')

const inc = source$ => Observable.create(observer =>
  source$.subscribe(
    value => observer.next(value + 1),
    err => observer.error(err),
    () => observer.complete()
  )
);

const dec = source$ => Observable.create(observer =>
  source$.subscribe(
    value => observer.next(value - 1),
    err => observer.error(err),
    () => observer.complete()
  )
);

const noop = source$ => Observable.create(observer =>
  source$.subscribe(
    value => observer.next(value),
    err => observer.error(err),
    () => observer.complete()
  )
);

of(1).pipe(
  expand(x => (
    from([inc, dec, noop])
    	.pipe(
        mergeMap(operation => of(x).pipe(operation, delay(Math.floor(Math.random() * 50)))),
        first(),
        zip(click$),
        map(([x]) => x)
      )
  ))
)