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.

I've used CC with TypeScript, JavaScript and Python. Imo TypeScript gives best results. Many times CC will be alerted and act based on the TypeScript compile process, another useful layer in it's context.