Beautiful JavaScript

CHAPTER FOURTEEN

Functional JavaScript

Anton Kovalyov

Is JavaScript a functional programming language? This question has long been a topic of great debate within our community. Given that JavaScript’s author was recruited to do “Scheme in the browser,” one could argue that JavaScript was designed to be used as a functional language. On the other hand, JavaScript’s syntax closely resembles Java-like object-oriented programming, so perhaps it should be utilized in a similar manner. Then there might be some other arguments and counterarguments, and the next thing you know the day is over and you didn’t do anything useful.

This chapter is not about functional programming for its own sake, nor is it about altering JavaScript to make it resemble a pure functional language. Instead, this chapter is about taking a pragmatic approach to functional programming in JavaScript, a method by which programmers use elements of functional programming to simplify their code and make it more robust.

Functional Programming

Programming languages come in several varieties. Languages like Go and C are called procedural: their main programming unit is the procedure. Languages like Java and SmallTalk are object oriented: their main programming unit is the object. Both these approaches are imperative, which means they rely on commands that act upon the machine state. An imperative program executes a sequence of commands that change the program’s internal state over and over again.

Functional programming ...