Adonis is the best JS framework I've used, and the documentation is very sparse, and I had to lean a lot on the community . That said, it really makes it easy and fun to build web apps.
I've started using Phoenix on Elixir in the past few days, and it has been awesome! It is advertised as Rails/MVC without the compromises. It supports JSON API without HTML first class, and there are some great tutorials on using it with for example Phoenix, Apollo, GraphQL and Vue. The documentation is amazing (tons of examples and thourough. Coming from JS, the language syntax isn't very difficult at all, and from Rails it is even easier. One of the main selling points is 2-4x faster than Node Js depending on clustering, and a whopping 10x faster than Rails or similar python equivalents. It is only beat out by much more low level languages like Java, Go, Rust etc.
I haven't gone too far with Phoenix+Elixir yet, but it seems like it is much better than Node JS for building MVC/structured backends.
Great to hear about your experience with both Adonis and Elixir. I think that Elixir (once you get over the hurdle of picking up FP) makes it much easier than node to create robust and scalable apps, concurrency and reliability are built into the underlying platform, with node the burden is largely on the developer, I've experienced that first hand. Easy to crash or lock your app if you make a mistake.
The doubt I have about Elixir is not FP but the popularity of the platform, it's still quite a niche language. But, it has an active and enthusiastic community, great documentation, and the ecosystem around it isn't tiny, most of what you need seems to be there.
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