Hello all, I'm a professional web developer and live in JavaScript land. By night and by day, its my passion also my career.<p>Overall, I love JavaScript. But I want to invest my spare time in something else. Which languages would you recommend and can foresee having potential jobs around them in the next 15-20 years?
Don't learn a specific programming language. Learn programming.<p>The book you want is here: <a href="http://mitpress.mit.edu/sicp/" rel="nofollow">http://mitpress.mit.edu/sicp/</a>
Every language is essentially a fad. The newest fads are Julia, Go, and Rust.<p>Go forth and learn, if you want. But language doesn't matter, it's what you do and how you do it that counts.
Learn Clojure (and LISP).<p>If anything it will help you write better JavaScript (immutable data structures, functional programming, functional composition, ...)
It's good this isn't stackoverflow because this question would be closed in a heartbeat. I'm going to go completely against the grain here since you're asking about jobs and advise that you learn Java. You already know javascript, learning a second language will get you into the I'm a programmer and out of the I'm an 'X' programmer mindset.<p>All languages are a means to an end, through various routes and with various properties. Some are better suited to one set of problems than another.<p>Java may not be the most elegant language (to put it mildly) but it's a solid one and it gives you some interesting long term options such as to use your knowledge of the Java runtime and libraries by adding Clojure.
If your concern is job security, learn COBOL.<p>If you want to become a better programmer, to be flexible enough to write whatever software needs to be written over the next couple of decades, then diversity is important. Learn a Lisp. Learn a scripting language like Perl. Learn something low-level, like C or C++. Learn a line of business language like Java or C#.<p>Most software doesn't require mastery of a specific language, and having a broad background will mean you can adapt to whatever the future decides is 'in'. Learn a bit of everything.<p>Edit: Don't learn COBOL.
15-20 years is an incredibly long time in programming land. The only language I'm fairly certain will be around then is C. It's kind of a b*tch to learn, but once you do, it will certainly help you pick up other languages more quickly (seeing as many are written in C). I think your best investment, long term, would be to learn something very low-level like that; so it can help you interpret and understand the ever-changing world of high-level languages as time goes on.
On what platforms/systems do you enjoy building things for? Software/internet isn't going anywhere. Everything appears to be gradually shifting to mobile, but I still think websites will be just as important.
I agree with striking about Go and Rust. But I think Python and Ruby is not going anywhere soon. Most large systems still use Java (or Scala) right now so this is a good skill too