Historically, developers and designers have reached for JavaScript to build certain presentational features such as animations and transitions. With modern CSS features, some of these capabilities can now be achieved with little to no JavaScript. Reducing the JavaScript employed by your application can result in improved performance and helps establish a cleaner division between behavior and presentation concerns in your applications and pages.
This is a companion discussion topic for the original entry at https://upcase-production.herokuapp.com/upcase/videos/you-might-not-need-javascript