The way I look at it is to not jump on every new thing that comes along, but try to keep on eye on what's growing and what people are excited about. For me, at

The way I look at it is to not jump on every new thing that comes along, but try to keep on eye on what's growing and what people are excited about. For me, at the moment, that means Angular and Node. Four years ago it was Rails and Backbone. I'm keeping an eye on React, but am not ready to jump on that bandwagon yet. Lots of people may suggest Haskell, Scala, Go, Ember, React, etc. etc. and I may add one or two of those in the future, but at this point, I don't see enough broad interest in those languages to make it on my list yet. Keep an eye on job postings and you'll see trends in languages and frameworks growing.