Refactoring JavaScript

Chapter 11. Functional Refactoring

Of all the styles of JavaScript you can write, this one probably draws from the deepest well. Functional programming is older than object-oriented programming and even imperative programming. We’re going to take a few drinks from this well, but try to avoid falling in. FP has so much history and theory behind it that we have to set some boundaries.

There is an expression that “farmers don’t want to own all the land, just all the land their land touches.”

Learning functional programming in JavaScript has this same temptation. Here is a list of statements that might hold true for some people, but are not what we’re dealing with in this chapter:

• To learn functional programming, you need to learn Scheme/Haskell.
• To do “real” functional programming in JavaScript, you need to compile to JS from PureScript, TypeScript, ClojureScript, or something else.
• To learn functional programming, you need to learn the lambda calculus.
• To learn functional programming, you need to learn category theory.

A Confession

An implicit statement in the above is:

Evan needs to write this chapter as a 900-page book from the perspective of a Math/CS dual PhD (which he isn’t).

Sorry to disappoint, but that’s not going to happen in this chapter.

The focus here is entirely on the practical concern we’ve had all along: building confidence through developing and maintaining the interfaces of our code. To that end, we’ll be covering five main topics:

• The restrictions and benefits ...