I have had some experience with Java and Javascript. I have planned to learn a bit of Python, but haven’t gotten around to it. The hard part for me is I don’t know if either langauge to would limit what I would want to do. I have heard from a group of people that JavaScript/Node.JS would be better due to the fact that it’s a internet/server type of application, but do not know if this is true.
If Java and Javascript would equally be helpful and wouldn’t limit what I was trying to build, I’d learn towards Java as there are many public IRC libraries I could use for reference, and haven’t seen too many for JavaScript.