I think this kind of thing will be much more common now that WebAssembly is allowing other languages to compile to the browser. The nice thing about Java, is that there is already support for a dozen platforms, with full native support. The browser is just natural - Oracle should have done this years ago (provide a standard solution to compile to JS and now WASM).

We did. It was called GWT and it was aweful. Lets not.

GWT has its strengths (it's been doing the equivalent of tree-shaking and dead code elimination since 2006).

I use it daily at work. It's an impressive feat of engineering with a lackluster ecosystem and inconsistent documentation. Although it's not dead yet (at least technically) as it still has (slow) active development happening.

What is your opinion on the compile time though? No matter how I feel about what it actually can do I just can NOT get over the compile time.

In my day to day there's about 30 seconds for a cold compile (which is rare, only when I clear byte caches) and maybe 5 seconds usually, less if I've just changed one line or something small like that.

That said we're not using GWT for CSS, so that reduces iteration time where it's most noticable.

With TeaVM, I can do all my iterative development on the JVM (instant compile time). Compiling to the browser is usually just a one time thing for deployment. Although, TeaVM also have a "dev-server" mode that does iterative compiles, which is apparently much faster for iterative development.