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cc @salier, @yungsters for a sanity check before going further

Seems reasonable, but agree with @zpao.

if (typeof document === 'undefined') {
  return null;
}
// ...

Hello, early return makes sense, thanks. Pushed new commit into my branch. Please review.

Should I squash the commits or is it fine?

Squashing is ideal. :)

Soon, we will be able to automatically squash. But for now, manually squash is desired. Thanks!

Squashed and forced push.

Tell me more about the automatic squash, is it desired to have each PR squashed into single commit? Or is it going to be on demand, wherever sensible?

I'm in the process of getting this project automatically synchronized with our internal repository at Facebook. This is how Relay and React Native currently work.

Once that happens, each merged PR will automatically be squashed into one commit.

Thanks a lot, @yungsters and what is the process of releasing React. When should I expect this PR be part of it?

We'll push out a new fbjs version from here soon and then update the React dependency. 0.14 should be going out soon and I'll make sure it includes this.

This got reverted in 03ce16e . Was that intentional? Upon upgrade to React 0.14.5, I'm getting many errors that look like this while running unit tests. These errors are not present in React 0.14.4

     ReferenceError: document is not defined
      at getActiveElement (node_modules/react/node_modules/fbjs/lib/getActiveElement.js:25:12)

No, I don't think that was intentional. @yungsters - it looks like we never pulled this commit internally after merging :(

Acckkk... I'll re-commit this.

Sorry, but I am planning to to pull this out. When we add type checking to it becomes clear that the vast majority of facebook's code would not be prepared for this value to be undefined. Also this is basically an alias for writing document.activeElement, which is not something that should be written when there is no document. React itself has a lot of code which will run when document is not defined, and checks should be done there by checking the ExecutionEnvironment.canUseDOM property when appropriate. I have looked through React in an attempt to determine if any current usage of getActiveElement could possibly be called when document is undefined, but I don't see any.

If you can provide your a way that I can reproduce your issue I will ensure that it stays fixed, otherwise I will assume that in the last year React fixed the root cause of the issue.

Go ahead, should be fine :) Thanks for asking.