Arnav Aggarwal

Full-Stack Developer

React Ecosystem Setup — Step-By-Step Walkthrough

Published Jul 05, 2017Last updated Jan 01, 2018

Understand what React, Webpack, and Babel are doing and how to configure them yourself

This article was originally published on Medium.

React is arguably the hottest framework currently used by the web development community at this point. Unfortunately, for newcomers and even more seasoned developers, setting up the industry-standard React development environment for the first time is difficult, daunting, and frustrating. There are boilerplates such as create-react-app readily available for people who want to skip configuration and get started, but using them doesn’t provide insight into what’s actually going on.

This article is meant to take you through the setup process while teaching you as much as possible about what you and the tools you’re using are doing. The technologies we’ll discuss are what the React community has decided to embrace in the front-end ecosystem and what you’ll see professional developers and industry leaders using. It’s also what you’ll see in most examples online. There’s a whole ton of more tools and configuration purposely left out as this is meant to be a bare-bones beginners’ guide.

To see what we’ll be working towards or if you just want a boilerplate, go to:

arnav-aggarwal/react-setup-tutorial

This article requires elementary proficiency with HTML, Javascript (including very basic ES6 syntax), CSS, Node, and preferably Express. If you can make a to-do app, you’re ready for this. Let’s get started.

I’m using npm v 5 and Node v 8. If you’re using an older version of Node you should be fine. npm 5 saves dependencies to your package.json by default without the need for a flag, so if using npm 4 or below, make sure to use --save when installing production dependencies. I’d recommend upgrading to npm 5. It’s faster and locks down your dependencies with a package-lock.json file, denoting every version of every dependency. You can use Webpack 2 or 3 — both should work.

Initial Configuration

Let’s set up a very basic file system. Run npm init and get a package.json. In our project’s root directory, let’s create a file called server.js and a folder called dist. dist is where we will store all client-facing code. In dist, create an app.html file. Make sure your file structure looks like this.

project_root
|
|---dist
|    |
|    |---app.html
|
|---package.json
|---server.js

The file structure can also be viewed here.

Basic HTML File

Let’s write to our dist/app.html file. Note that we have a div with an ID of container in the body, containing only the word ‘React’.

<!DOCTYPE html>
<html lang="en">
<head>
    <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>React - Basic Setup</title>
</head>
<body>
    <div id="container">React</div>
</body>
</html>

Basic Express Server

Run npm install express. You’ll get a package-lock.json if using npm 5. In server.js, we’ll write some code to get a basic Express server up and running. If you’ve set up an Express server before, this shouldn’t be new. If you haven’t used Express, it’s not critical to learning React. Just know that this creates a server on port 8080 and serves up dist/app.html.

const express = require('express');
const path = require('path');

const app = express();
const port = process.env.PORT || 8080;

app.set('port', port);
app.use(express.static(path.join(__dirname, './dist')));

app.get('*', (req, res) => {
    console.log('Serving ', req.url);
    res.sendFile(__dirname + '/dist/app.html');
});

app.listen(port, () => console.log('Listening on port', port));

Run npm start(an alias for node server.js). You should see something like this.

Verify that the server is working by going to localhost:8080. You should see the word ‘React’ on the page. Awesome, we have a basic HTML file and server!

You should have these changes.

Webpack

Common practice in the React ecosystem is to bundle all of the Javascript and CSS files we write into one big file. Webpack is the tool for the job. During the bundling, we’ll have webpack perform some more actions.

It’ll resolve our dependencies by going into the modules we import and concatenating those, pulling them out of our node_modules and putting them at the top of our single file. It’ll recursively go through every dependency and the dependencies’ dependencies, resolving all the way down.
It’ll transpile our farm-fresh, cutting-edge ES6+ down to ES5 so that it’ll work on virtually every browser.
It’ll minify our code by removing whitespace and shortening variable names, reducing the final file size.

In the end, we’ll be able to write modular, modern Javascript and CSS that we can work with easily and use best practices on.

Getting Started

Let’s create a folder named src in our root directory. This will contain all of our site’s Javascript and CSS. We’ll start with the Javascript. Put a file called index.js into src. In src/index.js, put a single line of code:

console.log('Testing our bundle');

With webpack, src/index.js will be our starting point, or entry point. Webpack will start with that file and generate our bundle. Let’s install webpack:

npm install -D webpack

Webpack requires a configuration file called webpack.config.js. Let’s create this file in our root directory. Excluding node_modules, our file structure now looks like this.

project_root
|
|---dist
|    |
|    |---app.html
|
|---src
|    |
|    |---index.js
|
|---package.json
|---package-lock.json
|---server.js
|---webpack.config.js

webpack.config.js needs to export a configuration object that tells it where to start bundling and where to put the bundle. Add this into the file.

const path = require('path');

module.exports = {
  entry: path.resolve(__dirname, './src/index.js'),
    output: {
    	path: path.resolve(__dirname, './dist'),
    	filename: 'app.bundle.js'
    }
};

What our configuration object is telling webpack to do is to start at the entry point, src/index.js. It’ll go into that file, resolve all dependencies, and bundle them into the output path provided, the folder dist. It’ll name the new bundled file app.bundle.js.

Go ahead and run

webpack

on the command line and see what happens.

Done? Good. You should see app.bundle.js magically appear in your dist folder. Go ahead and run

node dist/app.bundle.js

You should see ‘Testing our bundle’ log on your Node console. Congratulations, you’ve created your first webpack bundle!

If using git, you’ll want to add dist/app.bundle.js to your .gitignore. We only want to keep track of the source files, not the generated bundle.

Eventually, we’re going to want to run the code in this file to render our app to the DOM. Let’s add a script tag in dist/app.html.

<!DOCTYPE html>
<html lang="en">
<head>
    <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>React - Basic Setup</title>
</head>
<body>
    <div id="container">React</div>
</body>
<script src="app.bundle.js"></script>
</html>

If you open up dist/app.html in the browser, you’ll now see the ‘Testing our bundle’ statement log to the browser’s console.

At this point you should have added these changes.

Flags

Right now, nothing is being minified. Open up dist/app.bundle.js and see what’s inside if you like. To make webpack minify your code, use the production flag, -p. Type in webpack -p and look at the bundle file. You’ll see one long line of unreadable code with all unnecessary whitespace removed. It’ll look something like this.

Let’s go back to our non-minified code for a second. Type in webpack to generate the non-minified bundle. An issue with using a bundle instead of our source code is that it makes debugging more difficult, because the stack trace now refers to our bundle file. If we open our HTML file in the browser now, we’ll see this:

The stack trace for the console.log statement tells us to go to app.bundle.js, line 73. That’s not very useful. We want the stack trace to show our files correctly.

We need a source-map — a way to tell the browser to display errors and logs according to the source and not the final bundle. A source map adds a considerable amount of code, so the file size will be larger. This is fine for production. Using the development flag,-d, will tell webpack to generate a source map for our code. Go ahead and run

 webpack -d

Now, we get a better log. We can actually see that it comes from line 1 in index.js.

While developing, it’s not fun to have to type webpack over and over again. Using the --watch flag during development means webpack will watch our files and re-generate the bundle every time we save a change. During development, we’ll want to use both the development flag and the watch flag, so our command will be

 webpack -d --watch

Every time you change webpack.config.js, you’ll need to kill the watching process and restart webpack for the changes to affect your bundle.

Babel

I mentioned earlier that we want to be able to use new, shiny ES6 code while making our sites cross-browser compatible. Babel is the library we’ll use to transpile our code, and we’ll configure webpack to do it when we run webpack.

Go ahead and install these three dependencies.

npm install -D babel-core babel-loader babel-preset-env

Babel-core is a library that takes in code as a string and transpiles it down.
Babel-loader is what allows us to tie babel-core into webpack and lets webpack’s configuration know to use the babel-core library.
Babel-preset-env is essentially a configuration for babel which lets us pass in options. Without the options, it uses defaults, which means it will understand code up to ES2017 standards and transpile it down to ES5.

There are a number of ways to configure webpack with babel and we’ll just pick an easy one. You’ll need to add some code into webpack.config.js.

const path = require('path');

const path = require('path');

module.exports = {
    entry: path.resolve(__dirname, './src/index.js'),
    output: {
        path: path.resolve(__dirname, './dist'),
        filename: 'app.bundle.js',
    },
    module: {
        rules: [
            {
                test: /\.js$/,
                exclude: [/node_modules/],
                use: {
                    loader: 'babel-loader',
                    options: {
                        presets: ['env']
                    }
                }
            }
        ]
    }
};

This code is telling webpack to test the files in our directory and look for the filenames matching the regex in the test property. /\.js$/ is looking for files ending with .js, so it’ll find all of our Javascript files. We’re telling it to exclude our node_modules folder, because we don’t want to transpile that down, as all of our dependencies should already be written in ES5. Lastly, we’re telling it we want to use babel-loader, which links the babel-core library to webpack. We want to use the env preset, which works with ES2015, 2016, and 2017 code, so we can use the newest features.

Now we can use ES6 code and the bundle generated by webpack will contain only ES5 code.

Changes are here.

React

Let’s configure React. Run the following two commands. We’ll need react, react-dom, and babel-preset-react.

npm install react react-dom
npm install -D babel-preset-react

We’ll have to add a term to our webpack.config.js file to tell it that we’re writing React code.

const path = require('path');

module.exports = {
    entry: path.resolve(__dirname, './src/index.js'),
    output: {
        path: path.resolve(__dirname, './dist'),
        filename: 'app.bundle.js',
    },
    module: {
        rules: [
            {
                test: /\.js$/,
                exclude: [/node_modules/],
                use: {
                    loader: 'babel-loader',
                    options: {
                        presets: ['react', 'env']
                    }
                }
            }
        ]
    }
};

We’re telling Babel to use a special React preset. It’ll transform our React code into standard Javascript. But isn’t React just Javascript?? Not exactly. We’ll get to that.

You should be here.

Our First React Component

In src/index.js, delete the console.log statement and write the following code.

import React from 'react';
import ReactDOM from 'react-dom';

const container = document.getElementById('container');
const myDiv = <div>My First React Component!</div>;

ReactDOM.render(myDiv, container);

Start your server and webpack (use webpack -d --watch) to see what’s happening in your browser. Let webpack run in the background so we can continue to see our changes.

There’s a bunch of stuff going on here, so let’s break it down.

We can use import statements because webpack will resolve those for us. It’ll grab React and ReactDOM out of our node_modules and throw them at the top of our bundle, with the rest of our code below it.
We’re accessing the div with ID container for rendering our component. This is the DOM element that we’ll place our React elements in.
The next line, creating the variable myDiv, is the most exciting. We’re writing something that looks like HTML in our Javascript. myDiv is a variable that contains what we can think of as a DOM element that we just created.
The last line uses the ReactDOM library to render our myDiv element on the DOM.

Note that we import React, but don’t actually use it anywhere. This is because during transpilation, webpack and babel transform our code. That transformed code needs access to React.

To see what it finally turns into after webpack runs its magic, we can go to babeljs.io. The code below is the transpiled version of our five-line block above.

'use strict';
var _react = require('react');
var _react2 = _interopRequireDefault(_react);
var _reactDom = require('react-dom');
var _reactDom2 = _interopRequireDefault(_reactDom);
function _interopRequireDefault(obj) { return obj && obj.__esModule ? obj : { default: obj }; }

var container = document.getElementById('container');
var myDiv = _react2.default.createElement(
  'div',
  null,
  'My First React Component!'
);

_reactDom2.default.render(myDiv, container);

We need React in scope because our transpiled code needs access to it, even though we don’t directly use it ourselves. Note also that all ES6 features have been removed — import statements and constant variable declarations are transformed down to ES5.

Start the sever, run webpack, and go to localhost:8080. You should see what you expect. If we open your browser’s dev tools and inspect the text, we see our div nested inside the #container div present in our original HTML.

JSX

I said we’re writing stuff that looks like HTML. It’s not actually HTML. It’s something called JSX. JSX is something created by Facebook that provides an easy, mostly straightforward syntax to help us write React components. For the most part, it’s very similar to HTML, with a few key differences.

Start off writing a JSX component by writing something like you would in HTML. Instead of using the word class to denote the class we want to give our element, we need to use className. If we want to use Javascript while generating our element, we can use a pair of curly brackets to denote code that should be evaluated. Let’s type some more code into the babel repl and see how this works.

const out = 'outer';
const inn = 'inner';
const div = 'Div';
<div className={out + div}>
  <div className={inn + div}>
    <h1>JSX</h1>
    <span>Creating a JSX Div</span>
  </div>
</div>

This turns into:

'use strict';

var out = 'outer';
var inn = 'inner';
var div = 'Div';

React.createElement(
  'div',
  { className: out + div },
  React.createElement(
    'div',
    { className: inn + div },
    React.createElement(
      'h1',
      null,
      'JSX'
    ),
    React.createElement(
      'span',
      null,
      'Creating a JSX Div'
    )
  )
);

On the DOM, this looks like:

<div class="outerDiv">
    <div class="innerDiv">
        <h1>JSX</h1>
        <span>Creating a JSX Div</span>
    </div>
</div>

Refactoring the Component

First, let’s go ahead and delete ‘React’ from inside our container div in dist/app.html. After that, you should have these changes.

Let’s make it so src/index.js contains logic that only deals with rendering our app to the page. We want to abstract all the JSX into separate files. Let’s create a components folder in src. In there, let’s create a file called app.js that will contain the logic dealing with creating our site. All src/index.js should do is render our app to the DOM.

project_root
|
|---dist
|    |
|    |---app.html
|
|---src
|    |
|    |
|    |---components
|    |    |
|    |    |---app.js
|    |
|    |---index.js
|
|---package.json
|---package-lock.json
|---server.js
|---webpack.config.js

Let’s start by changing src/index.js a little bit. First, let’s grow our div a little bit. We’ll add an h1 and a span inside our div and we’ll rename myDiv to app.

import React from 'react';
import ReactDOM from 'react-dom';

const container = document.getElementById('container');
const app = (
    <div>
        <h1>JSX</h1>
        <span>My first JSX span!</span>
    </div>
);

ReactDOM.render(app, container);

We’re now going to move the app variable into a separate file. Export it from src/components/app.js. src/index.js should now look like this:

import React from 'react';
import ReactDOM from 'react-dom';

import App from './components/app';
const container = document.getElementById('container');

ReactDOM.render(App, container);

src/components/app.js should now have:

import React from 'react';

export default (
    <div>
        <h1>JSX</h1>
        <span>My first JSX span!</span>
    </div>
);

Again, we need React in scope even though we don’t apply it directly. Without it, the JSX wouldn’t work. If you omit the import statement, you’ll get an error saying React isn’t in scope.

If you refresh your page, you should see that nothing’s changed.

Exporting a Component

We’re going to turn app into a function that returns the JSX we want. We’ll explain why in a second. Change src/components/app.js into this.

import React from 'react';

export default function app() {
    return (
        <div>
            <h1>JSX</h1>
            <span>My first JSX span!</span>
        </div>
    );
}

Change src/index.js into this.

import React from 'react';
import ReactDOM from 'react-dom';

import App from './components/app';
const container = document.getElementById('container');

ReactDOM.render(<App></App>, container);

When we import a function that returns JSX, we can use that function as a new element, just like we use what we’re already familiar with. We’ve essentially defined a new element. We treat it like we would a div, span, h1-h6, etc, with an opening and closing tag. Using those opening and closing tags invokes the corresponding function and inserts the returned element in their place.

An empty tag can be self-closing. In other words,

<div></div> === <div />
<App></App> === <App />

We’ll be using this shorthand. You should be here.

That’s the basics of the basics. You’re on your way to learning React.

CSS

We want to be able to use stylesheets for our website. We need to add some babel configuration.

npm install -D style-loader css-loader

CSS-loader will resolve the import statements we use and concatenate CSS into our bundle. Style-loader will actually apply that CSS so we see it working on the page.

We also need to update webpack.config.js to tell it to import and transform our CSS files using these loaders.

const path = require('path');

module.exports = {
    entry: path.resolve(__dirname, './src/index.js'),
    output: {
        path: path.resolve(__dirname, './dist'),
        filename: 'app.bundle.js',
    },
    module: {
        rules: [
            {
                test: /\.js$/,
                exclude: [/node_modules/],
                use: {
                    loader: 'babel-loader',
                    options: {
                        presets: ['react', 'env']
                    }
                }
            },
            {
                test: /\.css$/,
                use: [
                    'style-loader',
                    'css-loader'
                ]
            }
        ]
    }
};

It’s fairly common practice to create a separate CSS file for each component, with only the CSS needed for that component present in that file. In src, add a styles folder. We’ll create src/styles/index.css and add our main CSS to that file. Let’s also create src/styles/app.css to store CSS specific to that component.

project_root
|
|---dist
|    |
|    |---app.html
|
|---src
|    |
|    |---index.js
|    |
|    |---components
|    |     |
|    |     |---app.js
|    |
|    |---styles
|          |
|          |---app.css
|          |---index.css
|
|---package.json
|---package-lock.json
|---server.js
|---webpack.config.js

In src/styles/index.css, we’ll add what we want to apply across the whole document.

html, body {
    font-family: sans-serif;
    background-color: #dddddd;
}

In src/styles/app.css, we’ll add CSS specific to the component.

h1 {
    color: #31416D;
}

With our webpack setup, we can import stylesheets directly. Add this directly below the import statements in src/index.js.

...
import App from './components/app';
import './styles/index.css';
...

And similarly, under the import statement in src/components/app.js:

import React from 'react';import '../styles/app.css';
...

With webpack running, if we refresh our web page we should see the styled changes.

The final changes are here. The complete repository is at:

arnav-aggarwal/react-setup-tutorial

Phew. That’s it.

Now you can focus on actually learning React. You should now understand enough of webpack to be able to change the configuration yourself in the future if need be. There are a ton of extra tools we can add — CSS preprocessors, testing frameworks, linters, other libraries such as redux and react-router. If interested, see my more thorough React boilerplate repository. But this will get you started.

If this was useful, please feel free to check out my other articles.

Arnav Aggarwal - Medium

Master Javascript’s New, Cutting-Edge Object Spread Operator

The Simple Rules to ‘this’ in Javascript

That’s it. Go learn React.

React Software Development Web development Webpack JavaScript

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Arnav Aggarwal

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3Replies

Zohair shaikh

7 years ago

One more may be useful for web design & development.<a herf=“https://www.j4jacket.com/sam-flynn-tron-legacy-jacket.html”>sam flynn tron</a>

Arnav Aggarwal

7 years ago

Hi Juan, glad you liked it. It’s general practice to use functions instead of classes wherever possible when writing components. Functions are more concise, easier to read, and faster. Components should only be promoted from functions to classes when necessary. If you need an internal state or access to something called lifecycle methods (functions used to alter component behavior), then you should promote your component to a class. Check out https://hashnode.com/post/when-should-i-be-using-functional-stateless-components-vs-react-class-based-stateless-components-ciuxxroxs003oj753yxzf3rlt for more information.

Juan Carlos Gonzalez

7 years ago

Hey Arnvav. Just read this article and it was extremely helpful. Thank you very much. I do have a question though. It became evident to me that during transpilation, webpack and babel transform code, and so you didn’t explicitly use of React.

My question is: what is the reason for defining React components as functions rather than using classes?