Prevent polling when browser is offline

[daneden]

I love useSwr! I’m using it to build a London Underground status site.

While testing the app on slow/no network speeds, I noticed that useSwr will continue polling endpoints even if the navigator is offline. This PR adds an additional boolean check in the tick function to ensure that requests aren’t sent if the browser is offline.

[sergiodxa]

Maybe it will be great to detect when the user is back online to trigger a revalidation.

[daneden]

I’m confused about why, but I’m getting an “Invalid hook call” error (as in Rules of Hooks) when I test this locally. I’m not sure if it’s an issue with different React modules being loaded; I’m also struggling to get tests to run locally, but it looks like tests pass in Travis!

Let me know if you also run into problems.

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Update: turns out the hook warning was indeed because of extraneous dependencies: this fix seems to work as intended after all 😊

[shuding]

Thanks a lot! Could you also create an option for it (same as config.refreshWhenHidden)? Because sometimes people use SWR for local states too so it can work in offline.

[daneden]

@quietshu no problem! Added as a config option. I also took @sergiodxa’s suggestion and added an additional revalidateOnReconnect option that will add an event listener to the online event and trigger a fetch.

[rauchg]

It just dawned on me we didn't have this capability. That's epic @daneden …

[shuding]

Thank you @daneden !

[shuding]

Published in swr@0.1.15 🎉