Limiting yourself to one language however wide spread it is, is damaging. It limits you way of thinking about problems and narrows your vision when designing solutions.
Don't get into the "It CAN be done in JS therefore it SHOULD be done in JS" mindset that many people on HN seem to share. Teach yourself to use different tools and always choose the most appropriate one for the task at hand.
I am a software developer in the UK and I have used C++, Python, Java, Lua and JS (all in the last 2 years) and all of them have their place.