Redux came to be a go-to solution for state management in React apps. It's also one of the most incomprehensible tools in the shed.

What is an application state?

To understand, how Redux works, first, we need to understand, what is an application state.

In the smallest scale, application state can be a simple flag:

const STATE = { API: "OK" };

This is a simple information that our API is available. Of course, this is very exaggerated example, and most of the time, states are far more complex. But in general, state is a collection of (internal) information available to the application.

Knowing this, we can move along, to the state manager.

What is a state manager?

State is nothing, if it is hardcoded. If you will simply define a flag with true, and never change it, it will be useless, because it won't reflect the actual situation. If our API will crash, we should be able to update the state with the fact.

In the simplest terms, it would look like this:

const STATE = { API: true };

const setApiState = (flag) => { STATE.API = flag };

This is, again, very simple example that you wouldn't find live (probably). But it illustrate the point – state needs to be managed. We need to be able to update it to reflect the current situation.

But writing is only a half of it. The second one is reading.

The whole point of having a state is to inform our entire application of it. So, if one of our services detects that API is down, it fires the setApiState(false) function, that we've declared before. And now, every other part of the app should be able to read it:

import { API } from "./state";

if (API) {
  fetch("...");
} else {
  alert("API is down");
}

This is a super simple of how the state can be used in both ways – writing and reading.

(Why) do I need this?

This is a question a few people ask. "Do I need a state manager?". Quite often you don't. Having your state managed is like having an internal mail department in your company. It's cool to have one, but is your five-guys-in-a-room startup really needs it?

Picture this situation: you want to know how is your legal department works. In scenario A, you have a mail department, in scenario B – you don't.

Scenario A: You write a letter, pass it to a mail department worker and await reply. Someone from the legal writes an answer, dispatches it the same route. You get the information. It says "It's okay".

Scenario B: You ask the legal guy, "hey, how's it going". He replies "It's okay".

Image this happens in two companies – small startup based in a single room and in a corporation with hundreds of employees around the globe. Which scenario fits which company?

Managing state is all about scale.

If your application has a lot of modules which "speak" with each other, you need a state manager. If you run a simple web page, you probably don't.

Conclusion

I hope I've shed some light on what Redux is and at least made you ask yourself "do I need it?". In the next part, I'll explain more in-depth how it works and why it adopted so well into the React ecosystem.