How to switch class for div using js? : <p>I've done this using jquery, but can't do it with js.</p>

<p>Look at my code:  </p>

<p>https:// jsfiddle. net/88pd6zj0/</p>

<p>It's working only with first class = "html", but not working with another.
I've tried change "querySelector" on "querySelectorAll" - and it's working no one class.</p>

<p>How to fix this problem? 
Thank you.</p>
