useSyncExternalStore

[00:00] Let's start by creating a getSnapshot function. So getSnapshot, and this is going to snapshot or return the matchMedia thing. So we're going to say window.matchMedia, and here is our media query.

[00:16] In fact, let's take this, and we'll just grab it from here. There we go. And here's our media query. So this is how we determine at any given point, is this value, does this query match? Great, so we don't have to store that anywhere.

[00:36] The browser stores it for us. We can just grab it at any time. Great, so now we can make a function called subscribe, which accepts a callback. It is just, we don't really care about what it returns or what the callback returns. We return our cleanup. And in here, we need to add an event listener on this match

[00:55] media thing. So let's add our media query list from window.matchMedia with our media query. And then we'll add a change event listener, and we'll just pass the callback. Just like here react, it changed.

[01:12] And from there, in our return callback, our cleanup, we can just say remove that event listener so we don't have any memory leaks or any of that problem. And that's it. We created a subscribe. We created a getSnapshot.

[01:28] So we are ready to use sync external store for our isNarrow state. Subscribe, getSnapshot, boom. And now, I am on a narrow screen. And if I grab this, I'm on a wide screen. Narrow, wide, narrow, wide, it's amazing.

[01:47] And it's all synchronized using just web platform, add event listener, and use sync external store. The external store is the browser. The browser has the state for the width, or specifically whether this media query matches. Works great.

[00:00] We've got ourselves a narrow screen notifier. So this text should change as the width of our screen changes. So that is your objective, is to make that work. And we're going to be using USYNC External Store to make that happen. You're going to use the MatchMedia API

[00:17] to have a media query that will tell us whether or not the screen is a certain width. And you can subscribe to this, and it's kind of cool. So feel free to dive into the MDN docs. Also kind of hand-holdy in some of the comments, because I'm not here to teach you MatchMedia.

[00:36] You can go learn that on your own time. I'm here to teach you how to use USYNC External Store, and that's what we're going to do in this exercise using Window MatchMedia. So have a good time. We'll see you in this exercise.

Advanced React APIs covers many of the React APIs that you might not see on a day-to-day basis but you will need these in your toolbelt for certain scenarios that pop up.

We'll take a tour of several advanced hooks and React API, their use-cases, and when to use them. 

These will include:

- useReducer
- use
- createContext
- useLayoutEffect
- useImperativeHandle
- useSyncExternalStore
- flushSync
- createPortal


## Complex State Management

First we'll dive into the deep-end of state management with `useReducer`. This hook comes in really handy when you feel the logic in your components is a sprawling mess and you'd like to consolidate that into a single place with a nice API to interact with. 

We'll get into some state optimizations as well as how to make your logic easily sharable throughout your application with custom hooks.

## Context

While context is often times something you will leave up to library authors, there are some cases where you want to expose values you need throughout your application. We'll build a context provider that will expose search params to our components on a blog search page with `use` (previously `useContext`) and `createContext`.

You'll also refactor this code to expose the context you create in a custom hook that will give us nice error handling when context isn't set up correctly.

## Portals

React gives us `createPortal` to render UI outside of the DOM tree structure that a component might sit in. This is useful for UI elements like modals or tooltips. We'll explore how to attach a tooltip to the `document.body` to ensure it's positioned where it needs to go.

## Layout Computations

If the logic that you are working with in a `useEffect` affects the how the UI looks, especially on first render, you'll want to `useLayoutEffect`. You'll work through an exercise where the client makes calculations on where to place a tooltip before rendering and see the difference when this is in a `useLayoutEffect`.

## Imperative Handles

`useImperativeHandle` is an escape hatch in React that lets you imperatively tell React what to do. This hook is typically paired with a ref (from `useRef`) where we want to expose imperative methods to developers who pass a ref prop to our components.

## Focus Management

`flushSync` is technically a 'de-optimization' because it forces React to re-render whenever you call it. This means you need to be very careful and know what you're doing when you use it.

The primary use-case for this API is focus management. When you have conditional UI that gets rendered based on various state conditions, you can `flushSync` to ensure elements are in the DOM to properly focus.

## Sync Exernal Store

There are some cases where we want to synce our React code with the external world and display different UI based on the state of the external world. This is where `useSyncExternalStore` is useful and lets you subscribe to external stores. We'll also touch on server rendering as this hook supports that use-case.

Learn the hooks and API that React has to offer for complex state management, sharing context throughout your app, focus management and more.

Advanced React APIs

Kent C. Dodds

React Fundamentals

React Hooks

React Suspense

Advanced React Patterns

React Performance

React Server Components

Epic React Pro

Advanced React APIs Intro

Intro to Advanced State Management

New State

Previous State

State Object

Action Function

Traditional Reducer

Real World

Dad Joke Break Advanced State Management

Advanced State Management

Intro to State Optimization

Optimize state updates

Dad Joke Break State Optimization

State Optimization

Intro to Custom Hooks

Hook Function

useCallback

Dad Joke Break Custom Hooks 

Custom Hooks

Intro to Shared Context 

Context Provider

Context Hook

Dad Joke Break Shared Context 

Shared Context

Intro to Portals

createPortal

Dad Joke Break Portals 

Portals

Intro to Layout Computation 

useLayoutEffect

Dad Joke Break Layout Computation 

Layout Computation

Intro to Imperative Handles

useImperativeHandle

Dad Joke Break Imperative Handles 

Imperative Handles 

Intro to Focus Management 

flushSync

Dad Joke Break Focus Management 

Focus Management

Intro to Sync External State 

Make Store Utility

Handling Server Rendering

Dad Joke Break Sync External State

Sync External State

Outro to Advanced React APIs

Advanced React APIs

Advanced React APIs

Transcript

useSyncExternalStore

Transcript