How to handle Samsung S-Pen button event in the browser (Javascript)?

I’m developing a web app for the Galaxy Tab S3 that allows the user to draw with a Samsung S-Pen. The S-Pen has a button on the side which I know can be used by native Android applications to perform various functions. However, I am having a hard time figuring out how to identify which event gets fired in the browser when this button is pressed (or even if an event is fired?).

I found nothing in the S-Pen SDK and I have tried out all of the PointerEvents and TouchEvents and I tried identifying an event here:

Does anybody know the name of the event or where I can figure this out?

(I cross posted this question from StackOverflow btw.:

S Pen events can be detected using S Pen Remote SDK ( on your Android apps. JavaScript support / Browser event is not available right this moment.

Thank you,