Let's start by getting a sense of the lay of the land. Redux, for all of its power, has a relatively small API footprint.

• applyMiddleware
• bindActionCreators
• combineReducers
• compose
• createStore

Yup, just five functions. We'll discuss each of this in due time. We'll start with one of the simple utility methods that come along with Redux.

compose

If we want to split hairs. It's actually less than that. compose() isn't exactly Redux-specific. It's just a helper function. compose takes a series of functions as arguments and returns a new function that applies each those functions from right-to-left (or, from last-to-first if you're like me and have trouble discerning right from left).

Let's say that we had a bunch of functions that each take a string and return a modified string.

const makeLouder = (string) => string.toUpperCase();
const repeatThreeTimes = (string) => string.repeat(3);
const embolden = (string) => string.bold();

(Yea, I just learned that some of those methods exist too.)

We could call them all like this:

embolden(repeatThreeTimes(makeLouder("hello")));

But, what if I wanted to pass this combined function around as an argument to another function or method? I'd have to do something like this:

const makeLouderAndBoldAndRepeatThreeTimes = (string) =>
  embolden(repeatThreeTimes(makeLouder(string)));

This is tedious. compose gives us a simple way to compose functions out of other functions.

const makeLouderAndBoldAndRepeatThreeTimes = redux.compose(
  embolden,
  repeatThreeTimes,
  makeLouder
);

You'll see a similiar utility in other libraries like Lodash and Ramda.

This is used as a helper when creating enhancers, which we'll talk about in the a more advanced workshop. For now, I'm just fulfilling my promises of demystifying the core API.