[Javascript Powerpoint API] How to get currently visible slide of slide show (in read mode)

Question

I am using the Office javascript API to create an Add-In. In the edit mode, I am able to set a handler that gets called whenever the selection of a slide changes.

Office.context.document.addHandlerAsync(Office.EventType.DocumentSelectionChanged, myHandlerFunction)

But this does not work when the user starts the presentation in the slide show mode because then the selection does not change but the shown slide does. I would like the add a handler to be called whenever the shown slide changes. Then I would like to get the id of the currently visible slide in the slide show (read) mode.
Is there a way to add such a handler or at least to access which slide is currently shown in the slide show (read) mode?

Thank you very much
Lukas

(PS: I am very new to this forum so I hope I posted the question to the correct forum. If not please feel free to move it to the correct one.)