In this problem, your task is to figure out how to manually re-render a component whenever state is updated.

Learn how to create your own render function that you can trigger whenever you need.

Manually Trigger Re-Renders

[00:00] So, the first thing that we're going to do is update the render function call to call render after sending the state. So, that's our objective, but we need to have a render function. So, unfortunately, we are not reacting. We cannot just say, hey, render this component. And so, we're actually going to re-render our entire application, which consists of

[00:19] just a single component. So, this will work out nicely for us. So, we're going to say render right here. We'll stick app.render in there, and then we're going to call render to kick things off initially. If we didn't do that, then we'd just end up with a blank screen. That doesn't do anything. So, we do have to kick it off for that initial render.

[00:37] But now that we have this render function, we can call it right here to trigger a re-render of our application. Now, it's still not working, but you'll notice that we are getting that console log in our render function body right here in our counter component. And so, that is working properly. We are triggering a re-render.

[00:55] The problem is that the count just isn't changing. I'll think about that for a little bit. We'll get to that in the next step. But this is getting us to trigger a re-render whenever the state changes. So, good job.

Component Doesn't Re-Render when State Updates

[00:00] Clearly things aren't quite working quite right yet, because when we click on this button, nothing is happening, and we want things to happen. So, your job is to make it so that we re-render. That's why nothing is happening.

[00:14] So technically, this state value is happening, and in fact, if I add this console.log new state, save this, then you'll notice, yes, we are calling that set state, and we're calling it with the right state.

[00:30] And in fact, if I say state, this is the actual value, then we are assigning it to the right thing. The problem is that we are not re-rendering, so every time I click on this, nothing is happening, because we're not rendering the counter again.

[00:47] So your job is to render the counter again, and this is still not going to actually fix the problem for us, but a console.log in here should actually run when you're finished, and that gets us one step closer to having a use state that actually works. So, let's get into it.

With a poor understanding of hooks, you get this lingering feeling that you're missing out on some potential. 

If you could just deepen your understanding of your tools, you'd gain another level of productivity. 

You could be using a variety of hooks and have the `eslint-plugin-react-hooks` plugin installed that keeps you on track. 

But, there's something missing. How is this all working?

`useState` and `useEffect` are your *most* fundamental tools in the hooks tool-belt. 

And like with all hooks, they follow these two rules:

1. Only Call Hooks at the Top Level
2. Only Call Hooks from React Functions

Why do these rules exist?

Learning the answer to this question is how you'll deepen your understanding. 

And the best way to do that is to jump in and build your own hooks!

In this tutorial, you'll be recreating `useState` and `useEffect` from scratch. 

And by the end, your brain will be its own `eslint-plugin-react-hooks`. Because you'll know exactly why the rules can't be violated. 

## What to expect:

**Recreate useState:** You'll be recreating your own version of useState. In the process you'll learn about how hooks preserve state, and manage component renders. 

**Support multiple hooks:** Learn exactly why hooks *must* be in a deterministic order and how multiple hooks are managed and persisted.

**Recreate useEffect:** Finally you'll apply what you learned to useEffect and learn how React stores the callbacks and diffs the dependency array. 

In this tutorial, you'll recreate useState and useEffect from scratch, learn essential rules, and understand how hooks manage state and renders.

Build React Hooks

In this workshop you'll be building your own versions of React Hooks without using any existing hooks!

Build React Hooks Introduction

Introduction

Introduction to useState

The goal of this challenge is to replace the useState the comes from React with your own. Then, just render the initial state.

In this solution, you'll learn how to setup a useState generic function and some of the type nuances that need to be considered. 

Create Your Own useState Generic Function

Render an Initial State

The goal in this problem is to make the setState function from your custom useState hook work. 

In this solution you'll work towards making your own version of the useState hook's setState function.

Reassign state to a New Value

Make the setState Function Work

In this problem, you will need to to figure out how to preserve state between renders.

Learn the steps you need to take to ensure that your state doesn't get overwritten by the initial state on each render.

Prevent State From Being Reset Each Render

State Is Reset to initialState on Each Render

Time to take a break before moving on to the next section!

Dad Joke and Break

useState

In this section you'll be breaking renders down into phases and supporting multiple hooks at once.

Introduction to Multiple Hooks

Explicitly define render phases so that it's clear what phase you are in on each render. 

In this solution, we go over the steps we need to take to allow multiple useState hooks to initialize their own state.

Explicitly Defined Phases

Multiple Calls to useState Breaks initialState

The initial state is working, but state is still being shared across useState functions.

We can use an index that is incremented on each call to useState to keep track of each instance's location in a states array. 

Track useState Hooks with a Hooks Index

All useState Hooks Are Overwriting the Same State

Refresh yourself and get ready for the next section!

Multiple Hooks

In this section, you'll be creating your own useEffect hooks!

Introduction to useEffect

We have a useEffect in place that we are importing from react. But, we want to get rid of that and create our own!

Time to lay down your first iteration of useEffect without the dependency array. 

Implementing Your Own useEffect

Replace React's useEffect With Your Own

Now it's time to tackle the dependency array. When an array is provided, the callback should only be called when the values change.

In this solution, you'll learn why you need to track and compare in order to implement the dependency array.

Build React Hooks

Build React Hooks

Transcript

Component Doesn't Re-Render when State Updates

Transcript