Building a modern react app from scratch in 2021

February 24th, 2021

This article was originally published on GitHub on the repo yakkomajuri/react-from-scratch under the name "Building a modern React app from scratch in 2021".

⏭️ Running as a boilerplate

If you want to use the react-from-scratch repo as a boilerplate, you can simply do:

git clone
cd react-from-scratch
yarn start

The app will be available on localhost:3000.

💪 Motivation

The main objective of this tutorial for me was to get myself to better understand the multiple moving parts that make a React app work, rather than just accepting the "magic" of the many templates/boilerplates out there, like create-react-app, and react-boilerplate.

It was very much inspired by the extremely well-written Creating a React App… From Scratch. by @paradoxinversion, an article that is so good it is referenced in the official React Docs.

However, times change, and I wanted to build a modern React app from scratch in 2021. As such, I had a few more "essentials" to include in the toolchain, and wanted to work with the latest versions of core libraries. In some ways, I see this as the latest version of the tutorial mentioned above.

🎯 Objective

My goal here is simple: build a React app from "scratch". From scratch here doesn't mean building the supporting tools myself, but rather taking responsibility for their setup, rather than outsourcing it to something like create-react-app.

However, beyond setting up a React app that just works, I also had a few more requirements, pertaining to what many would deem "essentials" of the modern stack:

  1. It must support TypeScript
  2. It should have state management provisioned out of the gate

⚒️ Tooling

So what exactly do I need to make this work?

To find the answer, I started with the React Docs.

Reading Creating a Toolchain from Scratch tells me the following about what I need:

  • A package manager, such as Yarn or npm. It lets you take advantage of a vast ecosystem of third-party packages, and easily install or update them.
  • A bundler, such as webpack or Parcel. It lets you write modular code and bundle it together into small packages to optimize load time.
  • A compiler such as Babel. It lets you write modern JavaScript code that still works in older browsers.

This short snippet tells me quite a bit about what I need and why I need it. So I made my picks:

These are pretty standard choices. Even if you haven't set these up yourself before, you've probably dealt with them, or at least heard about them at some point.

However, based on my requirements, I still have one thing missing - a state management library.

Redux would have been the straightforward choice, but I went with Kea. Kea is in fact built on top of Redux, so I'll effectively be using Redux under the hood, but it makes state management significantly easier.

For full disclosure, I am definitely biased - the reason for choosing Kea is simply that I use it at work, and its author is my co-worker.

⏯️ Getting Started

The first thing we need is a new directory. Set that up and then run yarn init inside of it to get started.

When it asks you for the "entry point", use src/index.tsx. You'll know why in a second.

Inside your directory, create 2 more: src and public.

src will host the entire source code for our project, while public will be where we put the static assets.

⚙️ Setup

Rather than being a one-size-fits-all tutorial, this is meant to be a learning process, and dealing with issues that arise is inevitably an important part of it.

Hence, I won't be tagging version numbers on installations. You can check the versions being used in package.json if you want to use this as a boilerplate.

As an example, I decided to use Webpack v5 for this tutorial, which brought me some compatibility issues with configs I was originally using from Webpack v4 projects. As always, with enough docs, articles, and StackOverflow posts, I got through it, and learned more in the process.


Getting Babel to work requires quite a few packages, you can install them like this:

yarn add --dev \
  @babel/core \
  @babel/cli \
  @babel/preset-env \
  @babel/preset-typescript \

babel-core is the compiler, the main thing we need.

babel-cli will let us use the compiler via the CLI.

The last three packages are Babel "templates" (presets), for dealing with various use cases. preset-env is used to prevent us from having headaches, allowing us to write modern JS while ensuring the output will work across clients. preset-typescript and preset-react are quite self-explanatory: we're using both TypeScript and React, so we'll be needing them.

Finally, we need to set up a babel.config.js file, specifying to the compiler the presets we're using:

// babel.config.js
module.exports = {
  presets: [


We want to use TypeScript in our project, so that has its own setup beyond the Babel preset.

First, we need the typescript package:

yarn add --dev typescript

Then, being proactive, I suggest you also get the following packages if you'll be following this tutorial until the end:

yarn add --dev @types/react @types/react-dom @types/react-redux

These packages contain the type declaration for the modules we'll be using throughout the project.

And we also need a tsconfig.json file - I'm using the config from here, which we use in production:

    "compilerOptions": {
        "baseUrl": "./src",
        "paths": {
            "types/*": ["./types/*"]
        "allowJs": true, // Allow JavaScript files to be compiled
        "skipLibCheck": true, // Skip type checking of all declaration files
        "esModuleInterop": true, // Disables namespace imports (import * as fs from "fs") and enables CJS/AMD/UMD style imports (import fs from "fs")
        "allowSyntheticDefaultImports": true, // Allow default imports from modules with no default export
        "strict": true, // Enable all strict type checking options
        "forceConsistentCasingInFileNames": true, // Disallow inconsistently-cased references to the same file.
        "module": "esnext", // Specify module code generation
        "moduleResolution": "node", // Resolve modules using Node.js style
        "resolveJsonModule": true, // Include modules imported with .json extension
        "noEmit": true, // Do not emit output (meaning do not compile code, only perform type checking)
        "jsx": "react", // Support JSX in .tsx files
        "sourceMap": true, // Generate corrresponding .map file
        "declaration": true, // Generate corresponding .d.ts file
        "noUnusedLocals": true, // Report errors on unused locals
        "noUnusedParameters": true, // Report errors on unused parameters
        "experimentalDecorators": true, // Enables experimental support for ES decorators
        "noFallthroughCasesInSwitch": true, // Report errors for fallthrough cases in switch statement
        "lib": ["dom", "es2019.array"]
    "include": ["src/**/*"],
    "exclude": ["node_modules/**/*", "staticfiles/**/*", "frontend/dist/**/*"]

Feel free to change some of the configuration above to better suit your needs. However, it's important that you keep these options:

"noEmit": true, // Do not emit output (meaning do not compile code, only perform type checking)
"jsx": "react", // Support JSX in .tsx files

"jsx": "react" is self-explanatory. As for noEmit, the reason we should have this as true is because Babel is compiling the TypeScript for us, so we just want typescript to be used to check for errors (e.g. while we're writing code).

Sidenote: Comments are allowed in tsconfig.json files


Webpack also needs a lot of stuff to work. Essentially, for every type of file we want to bundle, we'll need a specific loader.

Hence, here's what we need:

yarn add --dev \
    webpack \
    webpack-cli \
    webpack-dev-server \
    style-loader \
    css-loader \

webpack and webpack-cli follow the same principle as Babel - one is the core package and the other let's us access those tools from the CLI.

webpack-dev-server is what we need for local development. You'll notice that package.json never actually references it from a script, but it is required to run webpack serve:

[webpack-cli] For using 'serve' command you need to install: 'webpack-dev-server' package

Finally, the loaders are what we need for the different files we want to process. A ts-loader also exists, but, since we're using Babel to compile our JS files, we don't actually need it.

And, like with Babel, we need a webpack.config.js file:

// webpack.config.js
const path = require("path");
const webpack = require("webpack");

module.exports = {
  entry: "./src/index.tsx", // our entry point, as mentioned earlier
  mode: "development",
  module: {
    rules: [
        test: /\.[jt]sx?$/, // matches .js, .ts, and .tsx files
        loader: "babel-loader", // uses babel-loader for the specified file types (no ts-loader needed)
        exclude: /node_modules/,
        test: /\.css$/, // matches .css files only (i.e. not .scss, etc)
        use: ["style-loader", "css-loader"],
  resolve: {
    extensions: [".tsx", ".ts", ".js"],
  output: {
    filename: "bundle.js", // our output bundle
  devServer: {
    contentBase: path.join(__dirname, "public/"),
    port: 3000,
    publicPath: "http://localhost:3000/dist/",
    hotOnly: true,
  plugins: [new webpack.HotModuleReplacementPlugin()], // used for hot reloading when developing
  devtool: "eval-source-map", // builds high quality source maps


Given that this is a React app, we need some React packages too!

This should be enough:

yarn add react react-dom react-hot-loader

react is self-explanatory. react-dom will be used to render our app on index.tsx, and react-hot-loader is used for development - it will auto update our app on file changes.


Lastly, we need to set up our state management library, Kea.

From the Kea Docs, here's what you need:

yarn add kea redux react-redux reselect

We'll think ahead here as well and also grab us a separate package used when Kea logic is written in TypeScript:

yarn add --dev kea-typegen


With all this set up, we should add a few useful scripts to our package.json file:

    "scripts": {
        "start": "webpack serve --mode development",
        "typegen": "kea-typegen write ./src"

start will be used to run our server, and typegen to generate types for our Kea logic files.

💻 Finally, some React code

Quite a bit of setup, huh? I guess we should be thankful for boilerplates, especially when they manage all the dependencies and versioning for us (cough react-scripts).

Nevertheless, we're now done with setup, so onto some code!

But first, some vanilla HTML

The first thing we need is an index.html file, that React will use to render our app. It is the only .html file we'll have. This is also the only file we'll have in public/ in this tutorial.

Here's my index.html:

<!DOCTYPE html>
    <meta charset="UTF-8" />
      content="width=device-width, initial-scale=1, shrink-to-fit=no"
    <title>React from Scratch</title>
    <div id="root"></div>
    <noscript> You need to enable JavaScript to access this website. </noscript>
    <script src="../dist/bundle.js"></script>

There are a few things happening here:

  • We're setting a few default meta tags, as well as a title for our website
  • We specified a root div, which we'll use to render our App (this is essentially the starting point from which the inner HTML will be dynamically-generated by React)
  • We added a message for those that have JavaScript disabled, as our app won't work for them
  • We imported our finished Webpack bundle, which we haven't actually generated yet
    • This will contain all the code we write in a single file

The entry point

Remember the mention to entry point from earlier? Well now we've gotten to it. Go into the src/ subdir and make a new file called index.tsx.

Here's what I have in mine:

import React from "react";
import ReactDOM from "react-dom";
import { Provider } from "react-redux";
import { getContext, resetContext } from "kea";
import { App } from "./App";

  createStore: {},
  plugins: [],

  <Provider store={getContext().store}>
    <App />

There are 3 key things happening here:

  1. We're setting up Kea, which, like Redux, uses Provider to make the store available to any nested components (in this case, our entire app)
    • The resetContext call is not actually needed here, since we're not passing anything to it. However, I've left it here so you know where to add, for example, your Kea plugins, since you'll likely use those
  2. We're importing and rendering our App component (which we haven't built yet)
  3. We're telling React to render our app using our root div from index.html as the "binding point"

Our App!

Now, create a file called App.tsx, also inside src/, with the following:

import React from "react";
import { hot } from "react-hot-loader/root";
import { MyJSComponent } from "./components/MyJSComponent";
import { Counter } from "./components/Counter";

export const App = hot(_App);
export function _App(): JSX.Element | null {
  return (
      <h1>Hello world!</h1>
      <MyJSComponent />
      <Counter />

If you just want to see your app working at this point, you can remove the imports and references to MyJSComponent and Counter and run yarn start. This will start your server and you should be able to access your React app at localhost:3000, receiving your 'Hello world!' greeting from it.

The reason I've included these two extra components is to test that we have a few things working:

  1. We can write JavaScript alongside TypeScript
  2. Our state management is working fine
  3. Our bundler processes .css files with no problem (Counter has some minimal styling)

Hence, you could stop here if you wanted to. But if you want to see these 3 things in action, read on.

Writing JS and TS side-by-side

As you saw in our App.tsx file, we have a TypeScript file importing a JavaScript file with no problems.

The reason this works is because of this rule we have in webpack.config.js:

    test: /\.[jt]sx?$/,
    loader: 'babel-loader',
    exclude: /node_modules/,

Remove the j from test and we wouldn't be able to use JS files with TS files.

To test that everything is working fine, I simply created a tiny JS component and imported it into app.

I created it in a new directory called components/, and here's what it contains:

import React from "react";

export const MyJSComponent = () => <h2>Try out the counter below!</h2>;


The last thing I added to this project, while still keeping it minimal, is the traditional React counter component.

The goal here is to test that our Kea setup works, as well as that importing CSS files works too.

So, I first created a subdir inside components/ called Counter. Here I added 3 files:


Includes the actual component. Here it is:

import React, { useState } from "react";
import { useValues, useActions } from "kea";
import { counterLogic } from "./counterLogic";
import "./style.css";

export const Counter = () => {
  const { count } = useValues(counterLogic);
  const { incrementCounter, decrementCounter, updateCounter } =

  const [inputValue, setInputValue] = useState(0);

  return (
        <button onClick={incrementCounter}>+</button>
        <button onClick={decrementCounter}>-</button>
      <br />
          onChange={(e) => setInputValue(Number(}
        <button onClick={() => updateCounter(inputValue)}>Update Value</button>

Pretty simple stuff. Click + and the count goes up, - and the count goes down. Set any number using the input and count will be updated too.

Also notice the style.css import.


counterLogic.ts hosts the logic for manipulating the state that our Counter component uses. I won't explain how Kea works here, but the following is pretty self-explanatory:

import { kea } from "kea";
import { counterLogicType } from "./counterLogicType";

export const counterLogic =
  kea <
  counterLogicType >
    actions: {
      incrementCounter: true, //
      decrementCounter: true, // true is shorthand for a function that doesn't take any arguments
      updateCounter: (newValue: number) => ({ newValue }),
    reducers: {
      count: [
        0, // default value
          incrementCounter: (state) => state + 1,
          decrementCounter: (state) => state - 1,
          updateCounter: (_, { newValue }) => newValue, // ignore the state, set new value


Here I just have the most minimal styling I could think of, just to test that CSS is working as intended:

h3 {
  color: blue;

What about counterLogicType.ts?

Good question. If you explore the code in this repo you will see a counterLogicType.ts file inside the Counter directory.

This file is automatically generated by kea-typegen and contains the types for the counterLogic. It was generated by running yarn typegen, leveraging the command we added to package.json earlier. Usually, one shouldn't commit these files, since they're only useful in development, but I've left this one here so you can see what it looks like.

That's it!

If you've gotten all the way down here, hopefully you've come out of it with a shiny new React app, a modern boilerplate, and some additional knowledge. Honestly, this is just me documenting a bit of my learning process, but hopefully you got something out of it too!

If you have any feedback or suggestions, feel free to open an issue for it.