Maybe we should check for != null instead of typeof "undefined"

[rpearce]

I'm having an annoying issue where this all works locally but running with js-dom in travisCI, it can't find document (it's null), so this package breaks the tests, unfortunately.

Error: Uncaught [TypeError: Cannot read property 'scrollingElement' of null]

at calcScrollableElements (/home/travis/build/rpearce/react-medium-image-zoom/node_modules/focus-options-polyfill/index.js:41:18)

https://github.com/calvellido/focus-options-polyfill/blob/master/index.js#L3-L9

It might be a good idea to change those to be != null instead of typeof ... === "undefined". Using != null covers both undefined and null use cases. Another option would be simply to use the ! operator in front of each one.

What do you think?

[jonaskuske]

But I'm pretty sure that both the ! operator and != null will throw if document doesn't exist at all, e.g. in Node... So both typeof and one of these would be necessary..

Anyhow, why is JSDOM setting document to null in your setup? Isn't emulating document (and the rest of the DOM) basically the whole point there? 😅

[rpearce]

It seems I misspoke about js-dom; it throws an error while building the JS output in TravisCI, for there is no browser environment at the time the code is executed:
https://travis-ci.org/github/rpearce/react-medium-image-zoom/builds/680096939