Creating bundles with webpack

webpack is a bundler which means it is good at bundling things. Out of the box it only understands JavaScript’s import and require statements and because of that can just bundle JavaScript. If you give it an entry point1, it will start trawling through your code and bundle everything finds at import and require statements into one bundle2.

A very minimal webpack configuration file looks like this.

webpack.config.js:

 1const path = require('path');
 2
 3module.exports = {
 4  mode: 'none', // just to supress warnings for now
 5  entry: path.resolve('./src/main.js'),
 6  output: {
 7    filename: 'main.bundle.js',
 8    path: path.resolve('./dist/')
 9  }
10};
11

entry on line 5 tells webpack where to start trawling through the code. The output object on line 6 tells it in what directory to output the bundle and what to name it.

What happens if we give webpack the basic snippet of code below?

src/main.js:

1import { format } from 'date-fns';
2
3const formattedToday = format(new Date(), 'dddd DD MMMM');
4const p = document.createElement('p');
5p.textContent = `Today is ${formattedToday}`;
6
7document.body.appendChild(p);
8

This little code snippet depends on ‘date-fns’ which we will need to install using npm install --save date-fns.

With the provided webpack configuration above, webpack can start to bundle our code. On line 1, it will find the import statement for ‘date-fns’ which it will follow. ‘date-fns’ ended up in node_modules when we installed it, which is where webpack will find it because it knows how to deal with import statements. ‘date-fns’ itself contains many more require statements that webpack will dutifully follow until it has followed them all and pulled all code it found into one big3 bundle.

This bundle will be named and written in the directory as specified in the webpack configuration. In this case we will end up with a file named main.bundle.js in the dist/ directory of the root of our project.

That is how webpack does its bundling in a nutshell. Because it only knows about import and require it is not extremely useful out of the box. In the next article we will see how we can make it a lot more useful.


  1. As of webpack 4 if you do not provide an entry point, it will look for src/index.js. ↩︎
  2. If you give webpack more than one entry point you will end up with an equal amount of bundles. ↩︎
  3. In this case it is actually quite big because ‘date-fns’ is quite big and without any optimisation it will all get bundled. ↩︎