Polyfilling "isInFullscreen"

[khalyomede]

Hi, great script! You also might want to add this : https://stackoverflow.com/a/36672683/3753055, might be useful

[ethanius]

Hello, thanks. It actually needs a rewrite as I see it :)

Adding anything like that would be bloating the polyfill beyond the specification and in this case is completely unnecessary. To tell if fullscreen is active or not just look at the value of document.fullscreenElement.