I have done something similar. nderground is implemented using the Grails framework. Grails leverages Spring, Hibernate and Java Server Pages (although I’ll note JSP are more or less invisible most of the time).

I do use client side JavaScript. I have a license for the JavaScript Redactor editor, which allows nderground users to write and edit rich text like posts. I also have button automation, implemented in JavaScript, that supports editing.

One of the core features that nderground offers our users is privacy. So I have worked hard to make the site secure. This means that I limit the client side JavaScript to UI issues. All of the data filtering, validation and intelligence is on the server side, written in Groovy or Java. I have tried to follow the design idea that anything from the client cannot be trusted.

The result is that I have only a small amount of JavaScript on the client side, so a transpiled approach doesn’t seem worth it.