rx-paging.js

const getObservableAndNext = (baseUrl, firstPage) => {
  const subject = new Rx.Subject()

  const response$ = subject
    .flatMap(page => { return fetch(baseUrl, page) })
    .startsWith(firstPage)
  
  const data$ = response.map(response) => { return response.data })
  const page$ = response$.map((response) => { return response.nextPage })
    
  const next = () => subject.onNext(page$.last())
  
  return { data$, next}
}

const { data$, next } = getObservableAndNext('base_url', 0)
data$.subscribe(data => { 
  process(data)
  next()
})