An RxJS solution for a method utilizing an initial cache value and AJAX response on an interval to pass updated data to a subscriber.

cachedAjaxIntervalExample.js

fromCache('itemList')
.pipe(
  switchMap(itemList => (
    interval(3600000) // 1 hour
    .pipe(
      startWith(0),
      switchMap(() => (
        ajax({
          url: 'https://api.example.com/data',
        })
        .pipe(
          pluck('response'),
        )
      )),
      startWith(itemList),
      filter(Boolean),
      distinctUntilChanged(),
    )
  )),
)
.subscribe(itemList$)