How to deal with side effects in tree shaking code?

I've been trying to learn how to write code that is tree shaking friendly, but have run into a problem with unavoidable side effects that I'm not sure how to deal with.

In one of my modules, I access the global Audio constructor and use it to determine which audio files the browser can play (similar to how Modernizr does it). Whenever I try to tree shake my code, the Audio element and all references to it do not get eliminated, even if I don't import the module in my file.

let audio = new Audio(); // or document.createElement('audio')
let canPlay = {
  ogg: audio.canPlayType('audio/ogg; codecs="vorbis"').replace(/^no$/, '');
  mp3: audio.canPlayType('audio/mpeg; codecs="mp3"').replace(/^no$/, '');
  // ...
};

I understand that code that contains side effects cannot be eliminated, but what I can't find is how to deal with unavoidable side effects. I can't just not access a global object to create an audio element needed to detect feature support. So how do I handle accessing global browser functions/objects (which I do a lot in this library) in a way that is tree shaking friendly and still allows me to eliminate the code?

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