dan gaearon

## modern_js.md

      
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                Modern JavaScript in React Documentation
              
          
    If you haven’t worked with JavaScript in the last few years, these three points should give you enough knowledge to feel comfortable reading the React documentation:

We define variables with let and const statements. For the purposes of the React documentation, you can consider them equivalent to var.
We use the class keyword to define JavaScript classes. There are two things worth remembering about them. Firstly, unlike with objects, you don't need to put commas between class method definitions. Secondly, unlike many other languages with classes, in JavaScript the value of this in a method [depends on how it is called](https://developer.mozilla.org/en-US/docs/Web/Jav


## Classes.js
class Spiderman {
  lookOut() {
    alert('My Spider-Sense is tingling.');
  }
}

let miles = new Spiderman();
miles.lookOut();

## uselayouteffect-ssr.md

      
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                useLayoutEffect and server rendering
              
          
    If you use server rendering, keep in mind that neither useLayoutEffect nor useEffect can run until the JavaScript is downloaded.
You might see a warning if you try to useLayoutEffect on the server. Here's two common ways to fix it.
Option 1: Convert to useEffect

If this effect isn't important for first render (i.e. if the UI still looks valid before it runs), then useEffect instead.
function MyComponent() {

  
## connect.js
// connect() is a function that injects Redux-related props into your component.
// You can inject data and callbacks that change that data by dispatching actions.
function connect(mapStateToProps, mapDispatchToProps) {
  // It lets us inject component as the last step so people can use it as a decorator.
  // Generally you don't need to worry about it.
  return function (WrappedComponent) {
    // It returns a component
    return class extends React.Component {
      render() {
        return (

## 00-README-NEXT-SPA.md

      
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                / 00-README-NEXT-SPA.md
            
            
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                Next.js SPA example with dynamic client-only routing and static hosting
              
          
    Next.js client-only SPA example

Made this example to show how to use Next.js router for a 100% SPA (no JS server) app.
You use Next.js router like normally, but don't define getStaticProps and such. Instead you do client-only fetching with swr, react-query, or similar methods.
You can generate HTML fallback for the page if there's something meaningful to show before you "know" the params. (Remember, HTML is static, so it can't respond to dynamic query. But it can be different per route.)

Don't like Next? Here's how to do the same in Gatsby.


## slim-redux.js
function mapValues(obj, fn) {
  return Object.keys(obj).reduce((result, key) => {
    result[key] = fn(obj[key], key);
    return result;
  }, {});
}

function pick(obj, fn) {
  return Object.keys(obj).reduce((result, key) => {
    if (fn(obj[key])) {

## minification.md

      
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                gaearon
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              March 4, 2024 12:45
            
              
                How to Set Up Minification
              
          
    In production, it is recommended to minify any JavaScript code that is included with your application. Minification can help your website load several times faster, especially as the size of your JavaScript source code grows.
Here's one way to set it up:

Install Node.js
Run npm init -y in your project folder (don't skip this step!)
Run npm install terser

Now, to minify a file called like_button.js, run in the terminal:

  
## prepack-gentle-intro-1.md

      
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                A Gentle Introduction to Prepack, Part 1
              
          
Note:
When this guide is more complete, the plan is to move it into Prepack documentation.

For now I put it out as a gist to gather initial feedback.

A Gentle Introduction to Prepack (Part 1)

If you're building JavaScript apps, you might already be familiar with some tools that compile JavaScript code to equivalent JavaScript code:

Babel lets you use newer JavaScript language features, and outputs equivalent code that targets older JavaScript engines.


## index.html
<!DOCTYPE html>
<html>
  <head>
    <meta charset="UTF-8" />
    <title>Add React in One Minute</title>
  </head>
  <body>

    <h2>Add React in One Minute</h2>
    <p>This page demonstrates using React with no build tooling.</p>

## 16.3-blogpost-signatures.js
class Example extends React.Component<
  Props,
  State,
  Snapshot
> {
  static getDerivedStateFromProps(
    nextProps: Props,
    prevState: State
  ): $Shape<State> | null {
    // ...
	class Spiderman {
	lookOut() {
	alert('My Spider-Sense is tingling.');
	}
	}

	let miles = new Spiderman();
	miles.lookOut();
	// connect() is a function that injects Redux-related props into your component.
	// You can inject data and callbacks that change that data by dispatching actions.
	function connect(mapStateToProps, mapDispatchToProps) {
	// It lets us inject component as the last step so people can use it as a decorator.
	// Generally you don't need to worry about it.
	return function (WrappedComponent) {
	// It returns a component
	return class extends React.Component {
	render() {
	return (
	function mapValues(obj, fn) {
	return Object.keys(obj).reduce((result, key) => {
	result[key] = fn(obj[key], key);
	return result;
	}, {});
	}

	function pick(obj, fn) {
	return Object.keys(obj).reduce((result, key) => {
	if (fn(obj[key])) {
	<!DOCTYPE html>
	<html>
	<head>
	<meta charset="UTF-8" />
	<title>Add React in One Minute</title>
	</head>
	<body>

	<h2>Add React in One Minute</h2>
	<p>This page demonstrates using React with no build tooling.</p>
	class Example extends React.Component<
	Props,
	State,
	Snapshot
	> {
	static getDerivedStateFromProps(
	nextProps: Props,
	prevState: State
	): $Shape<State> \| null {
	// ...