React.js with ES6 & Webpack 4 => React-Hot-Loader 4 as Middleware with Express 4

To start a tiny react-app (with the new ES6 features) I wanted to have a basic hot-reload development server with an expressJS backend server, to handle API calls in the future.
This should be bundled with webpack because it’s the most popular and kinda easy to handle react in my opinion.

Since I couldn’t find any good documentation on the internet, I decided to put all of this together with the newest versions out there in 2018.

Many react apps are created with create-react-app nowadays. This is really easy to get started, but once you want to configure the build syste just a little bit, it’s time to eject the project. At this point it get’s confusing because many beginners cant handle the ejected code.

GitHub Repository

If you don’t wann see my config files or read any explanation, just go ahead and fork / clone my GitHub Repository to start your own react journey.

GitHub Repo

Starting your Server

The NodeJs server will compile the client via webpack and serve it.
There is no need for a second console which is serving the bundle via webpack.

$ npm start


Click me to see the full file!

This is the entry point of the project. Remember: the server will compile and serve the client.

    "main": "server/index.js"

The start script can be executed without the run parameter. We use nodemon to watch in our server directory for changes so the server is able to restart every time we change a file.
There is no need to watch in our client directory, that’s going to be done by webpack.
To enable our .babelrc file (ES6 support), we have to tell nodemon to execute the index.js with babel-node.

    "scripts": {
        "start": "nodemon --watch server --exec babel-node -- server/index.js",
        "test": "echo \"Error: no test specified\" && exit 1"

Normal dependencies.

    "dependencies": {
        "body-parser": "^1.18.2",
        "classnames": "^2.2.5",
        "express": "^4.16.3",
        "history": "^4.7.2",
        "path": "^0.12.7",
        "react": "^16.3.2",
        "react-dom": "^16.3.2",
        "react-router": "^4.2.0",
        "react-router-dom": "^4.2.2"

Build / development dependencies.

    "devDependencies": {
        "babel-cli": "^6.26.0",
        "babel-core": "^6.26.3",
        "babel-loader": "^7.1.4",
        "babel-plugin-react-html-attrs": "^2.1.0",
        "babel-plugin-transform-class-properties": "^6.24.1",
        "babel-plugin-transform-decorators-legacy": "^1.3.4",
        "babel-preset-es2015": "^6.24.1",
        "babel-preset-react": "^6.24.1",
        "babel-preset-stage-0": "^6.24.1",
        "nodemon": "^1.17.4",
        "open": "0.0.5",
        "webpack": "^4.8.3",
        "webpack-cli": "^2.1.3",
        "webpack-dev-middleware": "^3.1.3",
        "webpack-hot-middleware": "^2.22.1"


Click me to see the full file!

First of all we have to define a variable so we can change the config file depending on production or development mode.

var dev = process.env.NODE_ENV !== 'production';

Sourc maps will make our bundle.js way bigger. By choosing none in production mode, we can reduce the bundled js file by 90%.
Also the webpack mode will do some nice predefined steps for us like uglifying the code so it becomes even more reduced.

mode: dev ? 'development' : 'production',
devtool: dev ? 'inline-source-map' : 'none'

In developement mode we have to add the webpack-hot-middleware/client to our entry so react is able to accept the hot-reload.

entry: dev
    ? [
          path.resolve(__dirname, 'client/index.js')
    : [path.resolve(__dirname, 'client/index.js')];

As our module loader we use babel-loader so webpack knows how to handle ES6 code.

module: {
    rules: [
            test: /\.jsx?$/,
            use: ['babel-loader'],
            include: [path.resolve(__dirname, 'client')]

It’s very important to set the publicPath to / because that is the path where express will server the bundle.js file.

output: {
    path: path.resolve(__dirname, 'public'),
    publicPath: '/',
    filename: 'bundle.js'

We need to use these Modules to enable the Hot-Module-Replacement in development mode.

plugins: dev
    ? [
          new webpack.NamedModulesPlugin(),
          new webpack.HotModuleReplacementPlugin()
    : [];


Click me to see the file on GitHub!

All the presets for our ES6 support are going to be set here.
We also enable the new decorators to use @decorator later in our code.

    "presets": ["es2015", "react", "stage-0"],
    "plugins": [

react index.js

Click me to see the full file!

This code snippet needs to be added after the render() function in our react-app.
It accepts hot-reload requests from the browser.

if (process.env.NODE_ENV !== 'production') {
    if ( {;

express index.js

Click me to see the full file!

As before in our webpack config, we also have to define the development variable.
After that we can import all modules needed for our hot-reload plugin.
Even though we enabled ES6 code, it’s time to use the require, because ìmport statements can only be done at the top of the file.
Since we wrap these up in the if statement, they are not at the top anymore.

var dev = process.env.NODE_ENV !== 'production';

if (dev) {
    var webpackDevMiddleware = require('webpack-dev-middleware');
    var webpackHotMiddleware = require('webpack-hot-middleware');
    var webpack = require('webpack');
    var config = require('../webpack.config');

After setting up the express app we can use another middleware depending on the mode.
We inject the webpack-dev-middleware so express will compile and serve the bundle.js file.

if (dev) {
    const compiler = webpack(config);

        webpackDevMiddleware(compiler, {
            hot: true,
            noInfo: true,
            publicPath: config.output.publicPath


All set up! If you have any trouble getting this started, maybe so a fresh clone of the repository or feel free to contact me.

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