I'm thinking of leaning towards becoming a Full stack Javascript guy but not sure about the salary and demand for the language.
If you are interested in Enterprise, Java is probably still dominant.
JavaScript is a must for front end stuff but I can't say that a lot of companies will adopt it heavily for backend, particularly if most are already established on some stack they've already been working on.
My best recommendation without knowing much is go with Ruby and Rails.
Agency - Mostly PHP still but knowledge of Node is good (mostly for tools like Gulp). Occasionally see Ruby and Python in more design oriented agencies. Money is ok, and there's a lot of work out there.
Corporate - .NET, Java are all relatively popular. Java gets the best money because it's used extensively in the finance industry.
It seems pretty obvious, but a small minority of developers tend to see the world as black and white. Choosing a language that makes you happy is paramount, and if you're lucky you could end up as a C# programmer working at a startup, or as a PHP developer earning megabucks in the corporate world.
PHP/Python programmers with a sound understanding of JS/HTML/CSS and a familiarity with basic networking protocols that also have their wits about them in terms of basic UX/UI is the magic recipe that I am constantly looking for.
Larger/more complex/higher paying jobs usually require knowledge of multiple layers of the stack. It is really annoying when someone is able to knock out almost all of a project and then "I don't know how to do this..." when it comes to something outside of their scope.
I guess that is the difference between a hacker and a hack. A hacker will figure it out and add it to their own knowledge base knowing they have this information stored away for future use.
Every language that you learn and abandon, makes you understand the next one much quicker. Furthermore, you learn the appreciate the new constructs and idioms that new language brings. The new language usually also supports all the old constructs that you got used to in the past. So, you can always fall back on those too.
Concerning computer science, and especially compiler construction, indeed as you wrote, it applies equally everywhere.
After six years of relatively easy money of mostly delegating PHP work to others, I moved on to nodejs this year. I am not that keen on delegating node work at this time, because I want to play a bit more with it by myself.
Fair enough, to each his own. My time spent writing programs for the Apple II in the late 1970s, in 6502 assembly code, was largely non-transferable:
http://en.wikipedia.org/wiki/Apple_Writer
> Every language that you learn and abandon, makes you understand the next one much quicker.
Yes, I think that's generally true, with one possible infamous exception: BASIC as it once was, with line numbers and numeric GOTOs all over the place -- a real nightmare for large projects.
> I am not that keen on delegating node work at this time, because I want to play a bit more with it by myself.
It might be interesting to ask older programmers if they resisted getting into management simply because coding is such a pleasant occupation. We might find a lot of people unwilling to give up coding, even with a salary differential.