I’m teaching myself functional programming (FP). I first noticed it in Ruby, even though it’s been in JavaScript all along. I’m working my way through Structure and Interpretation of Computer Programs (SICP), and The Little Schemer books, so I’m learning Scheme and Lisp too.

When studying FP, I generally use JavaScript and Scheme. My FP examples here are usually in JavaScript:

  • It’s available everywhere, and most programmers are comfortable reading it.
  • It’s closer to Scheme than Ruby is, so the examples translate better. In fact, Douglas Crockford notes: “JavaScript has much in common with Scheme. It is a dynamic language. It has a flexible datatype (arrays) that can easily simulate s-expressions. And most importantly, functions are lambdas. Because of this deep similarity, all of the functions in The Little Schemer can be written in JavaScript.”

I include Ruby or Scheme, though, if it seems appropriate.

I often use the JavaScript Shell, or its big brother, the JavaScript Development environment, because I haven’t found or built a JavaScript REPL as nice as Dr. Scheme.


Most current JavaScript implementations are slow with recursion and closures…two cornerstones of functional programming.

I don’t worry about this, because my examples are not meant to be dropped into production systems without thought and testing. I write production-ready code at work; here, I play and explore. We do use some functional JavaScript where I work, but it’s where the performance is acceptable, and the imperative alternative would be too unwieldly.

History seems to show that performance is a short-term concern, and better programming techniques are a long-term concern. It also seems that there are no inherent reasons JavaScript is slow; more performant implementations may be in our future.

Why not Haskell or Erlang?

…or OCaml, Scala, F#, Clojure? I’m getting there. SICP and The Little Schemer books are more than enough for me right now.