Ruby and Python are certainly good first choices, but I don't think that Javascript is a bad choice. It may be rare on the server-side today but with the moment

Ruby and Python are certainly good first choices, but I don't think that Javascript is a bad choice. It may be rare on the server-side today but with the momentum it's building I think it may be a lot more common by the time a beginner is ready to write something non-trivial. Any working dev is going to have to learn Javascript sooner or later so you may as well start with it, IMO.