I tried different LLMs with various languages so far: Python, C++, Julia, Elixir and JavaScript.

The SOTA models come do a great job for all of them, but if I had to rank the capabilities for each language it would look like this:

JavaScript, Julia > Elixir > Python > C++

That's just a sample size of one, but I suspect, that for all but the most esoteric programming languages there is more than enough code in the training data.