refetchIntervalInBackground behaviour on mobile

[ikryvorotenko]

I'm trying to understand what would be the behavior of refetchIntervalInBackground flag on mobile devices. Like when the user switches the browser app or locks the phone.

As I understand, when the browser is not active, setInterval is not executed for refetch. Considering that, does it make more sense to have it implemented via timestamp in the state and custom refetchOnWindowFocus, like

const TTL = 20_000

useQuery({...
      refetchInterval: TTL,
      refetchOnWindowFocus: query => {
          const timestamp = query.state.data.timestamp
          const shouldRefetch = Date.now() > (timestamp + TTL);
          return shouldRefetch
      }
 }),

[TkDodo]

refetchIntervalInBackground checks for focusManager.isFocused, which you might need to implement differently in react-native: https://tanstack.com/query/v4/docs/react/react-native#refetch-on-app-focus

If the question wasn't about react native, but just browsers on mobile: focusManager is implemented with the visibilitychange event, so I think it'll work just the same as on a desktop