RxJs如何将两个重叠的可观察项合并为一个

const a = '-1-2-3-4-5-6-7-8-9-10-11-12-13-14-15';
const b = '-13--14--15--16--17--18--19-----20---------21--------------22------23--24';

const fromMarble = str => Rx.Observable.from(str.split('-')).concatMap(x => Rx.Observable.of(x).delay(1)).filter(v => v.length).map(x => parseInt(x));

const a$ = fromMarble(a).share();
const b$ = fromMarble(b).share();

const switchingSignal$ = Rx.Observable.combineLatest(a$, b$.take(1), (a, b) => a >= b).filter(x => x).take(1).share();

const distinct$ = Rx.Observable.merge(
	a$.takeUntil(switchingSignal$).map(x => x + '(from a)'), 
	b$.buffer(switchingSignal$).take(1).mergeMap(buffered => Rx.Observable.from(buffered)).map(x => x + '(from b$ buffer)'),
	b$.skipUntil(switchingSignal$).map(x => x + '(from b$)')
);

distinct$.subscribe(console.log);

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const a = '-1-2-3-4-5-6-7-8-9-10-11-12-13-14-15'
const b = '-13--14--15--16--17--18--19-----20---------21--------------22------23--24'
const fromMarble = str => Rx.Observable.defer(() => {
  console.log('side effect from subscribing to: ' + str);
  return Rx.Observable.from(str.split('-').filter(v => v.length));
});

const a$ = fromMarble(a);
const b$ = fromMarble(b);

const distinct$ = Rx.Observable.concat(
  a$,
  a$.last().switchMap(latest =>
    // .skipWhile + .skip(1) => skipWhile but inclusive
    b$.skipWhile(v => v !== latest).skip(1)
  ),
);

distinct$.subscribe(e => console.log(e));

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