How to Install React

Posted: javascript

Tsoding's recent stream about React is a hilarious reminder of the complications of web development tooling and the lack of support for beginners who want to take a bottom-up approach to learning.

What I found most surprising about his foray into React is actually the React documentation itself. It fails to provide any detail into setting up a React build environment yourself, instead recommending frameworks and tools that hide away the build mechanisms such that they're entirely opaque to the developer. For those who want to learn how things work from start to finish there's not much path forward, and it is all too easy to stumble onto old tools and processes that have been left to decompose after their fifteen minutes of fame.

For example, the documentation for Start a New React Project points developers towards Next.js or Remix, frameworks that I view as highly specialized and SSR-first. I can't believe that this is an acceptable starting point for a complete beginner, not only is React super complicated in and of itself, but to have to learn the abstractions of a meta-framework on top of that? Sounds like a nightmare! The Remix documentation alone offers a staggering number of APIs. Where does React end and the framework begin? How is a beginner supposed to know the difference?

It's also rather humorous how far React has moved away from its original goal of being "A JavaScript library for building user interfaces.". I know SSR is the bee's knees these days but I don't think it should be emphasized over the fundamental build processes that make the whole thing work.

In the days of yore, create-react-app was closer to this vision: run this CLI and bootstrap a React project that is just a regular React single page application. Nowadays Vite has effectively superseded this project, and its omission in the React documentation is surprising. Regardless, both of these projects still hide the details of the React build process behind a velvet curtain.

I do think it's important for beginners to familiarize themselves with some of the fundamental tools that drive their favorite frameworks. The new kids on the block like esbuild are super approachable and don't involve setting up convoluted Webpack configs or plugin pipelines. The rest of this post will demonstrate setting up a new React project with esbuild.

Why esbuild?

Why do we even need a build system in the first place? The answer is explained in more detail in the next section, but the primary reason is to support React's JSX syntax. Browsers don't know what JSX is, so we convert it to JavaScript beforehand.

Before esbuild, most developers were transforming JSX via the Babel JSX transform plugin together with a Webpack configuration that handled templating, static files, and other optimizations. Now you could go and install Babel manually, like Tsoding did in his stream, and use that instead for your new React project. However, Babel is both more complicated and slower than esbuild, so I don't think it's a good entrypoint for beginners.

The esbuild compiler source code is also a great read.

How to actually install React

Start by initializing a new npm project:

mkdir react-hello-world
cd react-hello-world
npm init -y

Then add your dependencies, React, ReactDOM, and esbuild.

Why are react and react-dom different packages? I can only guess at the intentions of the React core team, but my assumption is react-dom and react are separate packages to enable some of the non-browser React targets, like React Native. By shipping them in two packages, you can keep using react for your application's component/UI code, and easily swap in the react-dom/react-native entrypoints depending on whether you're building a web or mobile application. Since we're working with React in a browser, we'll need ReactDOM to configure the library to the DOM.

npm install react react-dom --save
npm install esbuild --save-dev

We use --save on React and ReactDOM because they're application dependencies, things that our application runtime actually depends on. We use --save-dev for esbuild since it's a development dependency, it's only needed to compile our application. This is a bit of a pointless distinction at this point, since we're going to compile our application into a static JS file anyway, but hey, best practice.

There are two pieces of boilerplate that we need to fill in next, the index.html webpage where our JavaScript is loaded, and index.jsx which contains the contents and initialization of our React application.

First index.jsx:

import { createRoot } from "react-dom/client";

const App = () => {
  return <h1>hello react</h1>;

const root = createRoot(document.getElementById("app"));
root.render(<App />);

And then index.html:

<!DOCTYPE html>
<html lang="en">
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>Hello, React</title>
    <div id="app"></div>
    <script src="./out.js"></script>

The important bit to note here is that the script tag in index.html is pointing to a file that is yet to exist: out.js. Normally JS doesn't require a build step (although when shipping to production it is a good idea for asset minification, among other reasons), but React is a special case because of the JSX syntax. JSX is not part of the ECMAScript specification and is therefore not known to the browser, so we have to add support for it by compiling our JSX code into plain old JS (hence esbuild).

In versions of React before the automatic runtime (which I'll get into in a second), JSX compilation looked something like the following.

This JSX:

// original.jsx
import React from "react";

function App() {
  return <h1>Hello World</h1>;

Is compiled to this JS:

// compiled.js
import React from "react";

function App() {
  return React.createElement('h1', null, 'Hello world');

In fact, you could write your entire app using the React.createElement API and avoid the compilation step (although in practice JSX is really why you're here anyway).

Nowadays the compilation situation is a little more complicated. Programmers found that repeating the import React from "react"; line at the top of every JSX file was onerous, so the ecosystem grew to support a JSX syntax that doesn't require it. This is known as the automatic JSX runtime.

Modern JSX is written without the import statement, like so:

// original.jsx
function App() {
  return <h1>Hello World</h1>;

And the compiled JS output is likewise changed to support this new syntax:

// compiled.js
import {jsx as _jsx} from 'react/jsx-runtime';

function App() {
  return _jsx('h1', { children: 'Hello world' });

The react/jsx-runtime is now imported as the responsibility of the compiler, not the programmer.

All this to say that we'll need to enable the automatic JSX runtime when we compile our index.jsx script into out.js. Luckily esbuild supports this out of the box.

Add the following build script to your package.json:

"scripts": {
  "build": "esbuild index.jsx --jsx=automatic --bundle --outfile=out.js"

The other point of note is the --bundle flag which inlines all of the dependencies needed for the application during the build. For our application, that means esbuild will insert React and ReactDOM from their respective node_modules/ into out.js during the build. out.js is referred to as a "bundle" (hence --bundle) because it now contains our application and all of its dependencies.

npm run build

After running the build, you can open up index.html in your browser and see your new React app in all of its glory.

What should new developers actually use when starting new projects?

Look, meta-frameworks like Next.js and Remix are rad. They bake in a ton of best practices and make it easy to deliver very complicated web applications while avoiding the pitfalls of a single page application. That said, I don't think they're a good place for a beginner to start.

Instead, poke around with the different build tools that underly these frameworks and learn how those megabytes of JS are actually delivered to your end users. Focus on learning the principles of React alone, and not the meta-framework glue that gives so many fancy features beneath layered abstractions.

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