I would suggest you to take a look at Vue; you can use it without any transpiler or heavy toolchain, just adding a good ol' script tag in your headers and voilà. The getting started guide [1] is awesome and translated to a gazillion of languages, so it also helps :)

I recommand Vue to any Javascript beginner that want to add interactivity to their page without having to handle the DOM manipulation themselves.

[1]: https://vuejs.org/v2/guide/