Webpack 4 tutorial: All You Need to Know, from 0 Conf to Production Mode

The webpack team is working hard on the next generation of the popular module bundler: webpack 4.

The following post is a living, breathing introduction to webpack 4. I’ll update it as soon as new info will come in. Stay tuned on my blog for more!

webpack 4 as a zero configuration module bundler

webpack is powerful and has a lot of unique features but one of its pain point is the configuration file.

Providing a configuration for webpack is not a big deal in medium to bigger projects. You can’t live without one. Yet, for smaller ones it’s kind of annoying, especially when you want to kickstart some toy app.

That’s why Parcel gained a lot of traction.

Sean and the webpack team are going to change that: webpack 4 doesn’t need a configuration file by default!

Let’s try that out.

Create a new directory and move into it:

mkdir webpack-4-quickstart && cd $_

Initialize a package.json by running:

npm init -y

Now let’s pull webpack 4 in.

npm i webpack --save-dev

We need webpack-cli also, which lives as a separate package:

npm i webpack-cli --save-dev

Now open up package.json and add a build script:

"scripts": {"build": "webpack"}

Close the file and save it.

Try to run:

npm run build

and see what happens:

ERROR in Entry module not found: Error: Can't resolve './src' in '~/webpack-4-quickstart'

webpack 4 is looking for an entry point in ./src! If you don’t know what that means go check out my previous article on switching from Gulp to webpack.

In brief: the entry point is the file webpack looks for to start building your Javascript bundle.

In the previous version of webpack the entry point has to be defined inside a configuration file named webpack.config.js.

But starting from webpack 4 there is no need to define the entry point: it will take ./src/index.js as the default!

Testing the new feature is easy. Create ./src/index.js:

console.log(`I'm a silly antry point`);

and run the build again:

npm run build

You will get the bundle in ~/webpack-4-quickstart/dist/main.js.

What? Wait a moment. There is no need to define the output file? Exactly.

In webpack 4 there is no need to define neither the entry point, nor the output file.

I know that for a lot of people that’s not so exciting. Webpack’s main strength is code splitting. But trust me, having a zero configuration tool speeds things up.

So here is the first news: webpack 4 doesn’t need a configuration file.

It will look in ./src/index.js as the default entry point. Moreover, it will spit out the bundle in ./dist/main.js.

In the next section we’ll see another nice feature of webpack 4: production and development mode.

webpack 4: production and development mode

Having 2 configuration files is a common pattern in webpack.

A tipical project may have:

• a configuration file for development, for defining webpack dev server and other stuff
• a configuration file for production, for defining UglifyJSPlugin, sourcemaps and so on

While bigger projects may still need 2 files, in webpack 4 you can get by without a single line of configuration.

How so?

webpack 4 introduces production and development mode.

In fact if you pay attention at the output of npm run buildyou’ll see a nice warning:

The ‘mode’ option has not been set. Set ‘mode’ option to ‘development’ or ‘production’ to enable defaults for this environment.

What does that mean? Let’s see.

Open up package.json and fill the script section like the following:

"scripts": {"dev": "webpack --mode development","build": "webpack --mode production"}

Now try to run:

npm run dev

and take a look at ./dist/main.js. What do you see? Yes, I know, a boring bundle… not minified!

Now try to run:

npm run build

and take a look at ./dist/main.js. What do you see now? A minified bundle!

Yes!

Production mode enables all sorts of optimizations out of the box. Including minification, scope hoisting, tree-shaking and more.

Development mode on the other hand is optimized for speed and does nothing more than providing an un-minified bundle.

So here is the second news: webpack 4 introduces production and development mode.

In webpack 4 you can get by without a single line of configuration! Just define the --modeflag and you get everything for free!

Stay tuned! More coming soon…

This is a living, breathing introduction to webpack 4. Stay tuned on my blog for more!

webpack 4: resources

A Github repo for the tutorial => webpack-4-quickstart

I know there’s already an awesome webpack list but here’s mine: a list of awesome resources about webpack 4 => awesome-webpack-4

Originally published at www.valentinog.com on January 19, 2018.