Functional programming is becoming more and more popular, and more and more controversial. JavaScript has functional properties, sure — you can treat functions as first order objects, using them to filter and transform lists, easily implement event-driven systems, or build reactive programs. But it wasn't designed to be a functional programming environment, not really — it does support recursion, but not as effectively as languages like Lisp or Erlang.
At any rate, even if you don't write functional JavaScript, you'll run into it during your career, and you should learn what to look for and how these systems work.
Knoldus organized a knolx session on the topic, Functional Programming In JavaScript, which covers the Functional Programming Paradigm In JavaScript.
You can watch the video of the session here:
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