Trigger an asynchronous action from an observable, and wait for it to complete before emitting another action.

example.js

function someEpic(action$, state$) {
  return action$.ofType(SOME_BEGIN).pipe(
    flatMap(begin => {
      return merge(
        of(actionCreatorForAsync()),
        action$.ofType(ASYNC_END).pipe(
          map(reduxRouterPush("/")) 
        )
      )
    })
  )
}