For serious apps it's impossible to escape reading Erlang or Erlang documentation. Many functions and libraries simply aren't available for Elixir or are partial (see `opentelemetry_*` family as an example). Deep debugging is almost exclusively done with Erlang functions.

I'd even say that the more serious/critical application becomes the more weight shifts toward Erlang. Personally I'd go with Erlang-first, but only because I've accumulated thousands paper cuts from Elixir.

For starters Elixir has much more palatable syntax, though.

It's very easy to call Erlang from Elixir,

    value = :erlang.function(a, b, c)

So with that in mind, you can just learn Elixir, use Erlang where you need it for some libraries. Elixir is IMO much nicer to learn, write and use. I think it is worth learning a bit about the underlying systems but I've never felt like I should have put in 10 erlang-only projects before writing larger elixir stuff.

Both! Right now the focus is on enabling rich UIs with pure Elixir running in the browser. But eventually Hologram could be able to act as an Erlang node in the cluster as well.

Thank you! The Elixir -> JS compiler is currently coupled with the framework - it's a custom thing, not a separate dependency.

Re the Gleam comparison: I don't know Gleam's implementation in detail so someone correct me if I'm wrong, but as I understand it - Gleam compiles to fairly readable JS with a minimal prelude, and deliberately treats the two targets as having different concurrency semantics. It doesn't try to replicate BEAM processes or OTP in JavaScript, instead using JS's native promise-based async. The upside is zero runtime overhead and clean JS interop.

Hologram takes the opposite approach - we're iteratively reimplementing the Erlang runtime in the browser, with the goal of having full semantic parity eventually. The tradeoff is a heavier runtime, but the benefit is that the same Elixir code can run on both server and client with consistent behavior.

I may be wrong but I believe the elixir->js compiler is currently built into the framework but it could potentially be separated in the future.

Gleam is different in that JS is a first-class target and built into Gleam's compiler, while Hologram is a standalone project.

Really appreciate it! Would love for you to give it another go - a lot has improved since then. If you run into any issues or have ideas for how things could be better, don't hesitate to reach out. Happy to help!

Not currently, but expanding to Erlang is definitely possible down the road. I've actually been considering adding an Erlang compiler since some Erlang functions that the Elixir standard library depends on could be compiled automatically instead of being ported by hand.