[development] Re-using collapsible.js for collapsible divs?

Hi there, my proficiency with JS is still near 0, so I need to ask the above question. In the past I used to use collapsible fieldsets to hide some content, but that is semantically wrong and maybe even invalid html. So I would like to have a collapsible div instead if fieldset. Anyy pointers on how to achieve this? I would prefer to not install extra JS. Cheers, Gerhard