fix: revalidateOnFocus not working on '< iOS 14'

[joshuakimDwan]

I found that revalidateOnFocus is not working on iOS 13.
To fix, window.addEventListener('visibilityevent', callback) should be replaced by document.addEventListener('visibilityevent', callback)

Ref: https://developer.mozilla.org/en-US/docs/Web/API/Document/visibilitychange_event

[codesandbox-ci]

This pull request is automatically built and testable in CodeSandbox.

To see build info of the built libraries, click here or the icon next to each commit SHA.

Latest deployment of this branch, based on commit b74ad97:

Sandbox	Source
SWR-Basic	Configuration
SWR-States	Configuration
SWR-Infinite	Configuration

[huozhi]

I think the 2 conditions doesn't have to be nested?

if (hasDocument) {
   // focus revalidators
}
if (hasWindow) {
   // other revalidators
}

[joshuakimDwan]

Does RN environment also have document object(like the web)?
I think that if RN doesn't have document object we should use window.addEventListener

[huozhi]

nope. it has window object but not document.
I double check again locally with a RN app. it shows that window doesn't have addEventListener. and we need to check addEventListener. looks like your first commit also works well and it's shorter

I'll approve it on my side if can be reverted to the previous commit. sorry for my mistake and thanks for the question.

[joshuakimDwan]

Aha. Is this logic ONLY for web, not RN?

[huozhi]

yes, swr supports browser runtime by default. since react is been ported to different rumtime, people are trying adopt swr along with react apps. I was wondering if it's possible to make swr more flexible to be adopted among runtimes. seems not easy.

[mikevercoelen]

After merging this fix, it's now crashing when debugging react native and giving:

document is not defined