Hello!

 I'm sort of new here and I was wondering if there was a way to upload a game just using a javascript file and the html file (index) so it would work as a browser game like some of the browser unity games I have seen on this site.

Thanks in advance :)))

Yep, you can, you just need to choose HTML in the "Kind of Project" dropdown and then upload a zip file.

Sure you can! Itch.io doesn't care what tools you make a web game with. Just put them in a ZIP archive together. Make sure to pick HTML under "kind of project" when you create the game page. After you upload your archive, tick the box below it saying "this file will be played in the browser", and you're all set.