A really great place to reach for this is Elixir/Phoenix now that the set theoretic type system is in place with LiveView. I have been doing some pretty large/complex codebases gradually working towards fully integrating working this way for the past 5 years and it has been great.

There's also Fable for F# but I believe this commenter is being sarcastic. Javascript is a common backend language.

Similar attempts include Scalajs.

The general challenge becomes integrating the fractional front-end code written in your backend-language that compiles to JS with the rest of the JS ecosystem.

JaneStreet have a love of writing their own stuff from scratch so it doesn't apply to them but it might to you.

Hence most people end up with frontend-as-backend rather than backend-as-frontend.

> Finally! I was waiting for this to become possible!

Sarcasm?

Do you want to have a talk as to why JaneStreet wasn't built on JavaScript?

I’m no UI expert - what’s wrong with the margins?

Basically most of Jane Street's published code[0] via its dependency on Core.

[0]: https://github.com/janestreet/bonsai/blob/f31661450eb133fe89...

They're a trading firm that hires really clever people to use math to trade. Their strategies are, presumably, very complicated and ever changing, and secrecy about them is the point - you get bigger margins for longer if people don't learn about your 'one weird trick' (that and also that there is presumably another side to your trades losing out on upside, and they might not be best pleased to learn about it.

Print money?

Market manipulation. They got kicked out and banned from the asian markets for fraud.

EDIT.

Janestreet PR team is downvoting. Like always, radio silence and just downvotes.

I had expected more from janestreet.

There was this submission two months ago: https://news.ycombinator.com/item?id=48365904 . Basically they have a TUI frontend for the same thing. And the blog post says: "Bonsai_term would feel familiar to anyone who’d ever done web development here, and it had the huge advantage of being especially amenable to AI assistance. It was actually somewhat of a mystery to us how good the models were at writing Bonsai_term code, given how relatively obscure it is [...]"

Probably not, because your agent won’t have much info about this tool in its training set.

If you read up on it that was basically India protecting its corrupt cronies. Janestreet showed severe problems with some Indian companies and instead of fixing that and creating a healthier and more transparent market they decided to go after the messenger.

There's a full terminal implementation of Bonsai as well. I actually use it in my personal workflow these days to manage my contacts database! https://anil.recoil.org/notes/aoah-2025-9

Been here 5 years, never saw it

HN is obsessed with anything done in niche programming languages, is my guess.

Ocsigen and Eliom were started 2005 and are pretty similar, although I can't find any well-known projects using Eliom :/.

Presumably this has learned some lessons from it, so it's probably better.

And there's nothing wrong with that. Many languages attempt to do the same thing. Why bother with 15 different languages if you can leverage one?

See also LiveView and Hologram for Elixir.

Agreed, looks like it's reinventing the wheels. Frameworks does not really matter today, AI agents write the code anyway.