Jonathan Petitcolas

Full-Stack Web Developer, Open-Source Contributor, Seasoned Speaker

Plugging Webpack to Jekyll Powered Pages

Published on 12 August 2016

I chose Jekyll to power this blog. It allows a blazing-fast display (as rendering is just composed of pure HTML static files) and a free hosting on GitHub Pages. Yet, when I started to build these pages a few years ago, I didn’t know about Webpack. Better late than never, let’s see how to plug these two powerful tools together.

Using Jekyll via Docker

Running Jekyll requires Ruby and some other dependencies. As I don’t need Ruby except for Jekyll, I prefer to use a Docker container. Thanks to Docker ecosystem, there is strong chances that someone already made an image fitting our needs. And, indeed, we can use starefossen/github-pages image:

docker run -v $PWD:/usr/src/app -p 4000:4000 starefossen/github-pages

We just run the image, exposing port 4000 to the outside world and mounting current working directory ($PWD) in the expected container source files location (/usr/src/app).

Let’s add this quite long command into our package.json file:

    // [...]
    "scripts": {
        "start": "docker run -v $PWD:/usr/src/app -p 4000:4000 starefossen/github-pages"

This way, instead of typing the previous boring command, we just need to type:

npm start

Setting Up Webpack

For our blog purpose, we have really basic needs: we just want to compile and compress some SASS files to a CSS single file.

First of all, let’s install all required dependencies:

npm install --save-dev \
    css-loader \
    extract-text-webpack-plugin \
    file-loader \
    sass-loader \
    webpack \

Webpack configuration is quite basic in our case:

var ExtractTextPlugin = require('extract-text-webpack-plugin');

module.exports = {
    entry: [
    output: {
        path: './build/',
        publicPath: '/',
        filename: 'build.js',
    module: {
        loaders: [
                test: /\.scss$/,
                loader: ExtractTextPlugin.extract('css!sass?outputStyle=expanded'),
                include: `${__dirname}/sass`,
                test: /\.(woff2?|svg|ttf|eot|png|jpe?g|gif|ico|pdf)?$/,
                loader: `file?name=[path][name].[ext]`,
                include: [`${__dirname}/sass`, `${__dirname}/posts`],
    plugins: [
        new ExtractTextPlugin('style.css', {
            allChunks: true,
    devtool: 'eval-cheap-module-source-map',

To sum up these lines, we compile every scss files in the sass/ folder into style.css file, taking into account every images in the sass/ and posts/ folders. If you are not familiar with this configuration, please refer to my Webpack introduction post.

Executing ./node_modules/.bin/webpack-dev-server should serve your stylesheet at http://localhost:8080/style.css.

Running Webpack Dev Server and Jekyll Concurrently

We now have two different servers. Launching them manually works fine, but it requires two different commands. Too cumbersome. So, let’s add a new dependency to our project:

npm install --save-dev concurrently

concurrently allows to launch two (or more) commands in parallel. That’s the perfect package for our purpose. We now just need to add a new command in our package.json file:

    "scripts": {
        "start": "concurrently 'docker run -v $PWD:/usr/src/app -p 4000:4000 starefossen/github-pages' 'webpack-dev-server --host='",

If we try to launch our project using the previous command, it would fail as $PWD is not translated to current working directory. That’s a concurrently issue I didn’t solve yet. Meanwhile, we can still hard-write our project path:

    "scripts": {
        "start": "concurrently 'docker run -v /home/johndoe/myproject:/usr/src/app -p 4000:4000 starefossen/github-pages' 'webpack-dev-server --host='",

That’s not optimal, but it works. Launching our project locally is now done using:

npm start

Updating our Jekyll Layout

We need to tell Jekyll to retrieve our stylesheet at correct location. It can be done easily modifying our main template (_layouts/default.html for this blog):

<link rel="stylesheet" href="http://localhost:8080/style.css" />

Or, for more flexibility, we can move the assets base URL into our _config.yml file:

assets_base_url: 'http://localhost:8080/'

Now, we can use this variable through the site object in our layout:

<link rel="stylesheet" href="{{ site.assets_base_url }}style.css" />

It works locally. Yet, when pushing our code to GitHub, we won’t be able to fetch our assets from localhost as the dev server won’t be started. Instead, we have to build our assets using webpack and use the generated build/style.css file.

So, we need to handle two different configuration files, depending our environment (dev for dev server, prod for built files). An easy way to handle it is to take profit of our Docker use, specifying our container two configuration files. Let’s override Jekyll launch parameters updating Docker run command:

    "scripts": {
        "start": "concurrently 'docker run [...] starefossen/github-pages jekyll serve --config _config.yml, -d /_site --watch --force_polling -H -P 4000'",

The only change here is we repeated the default command executed in Dockerfile adding it a --config parameter.

With this new parameter, Jekyll would fetch all configuration parameters from our _config.yml file, and override all parameters by those from file if they exist. So, we just need to create the file with following content:

assets_base_url: 'http://localhost:8080/'

And update our _config.yml file with:

assets_base_url: '/build/'

As GitHub considers only the _config.yml file, it would now work on both dev and production environment.

Enabling Live-Reload

Enabling live-reload is quite easy. We just need to add the built script to our layout:

<script src="/build/build.js" />

And add the two following options to our Webpack dev server call:

webpack-dev-server --inline --hot

Deploying our Pages

We still need to push our pages to GitHub gh-pages branch to deploy a new version of our website. However, we should not forget to rebuild Webpack assets. Let’s automate it adding a custom deploy command in our package.json file:

    "scripts": {
        "deploy": `
            webpack -p &&
            git add build/ &&
            (git commit -m 'Rebuilding assets' || true) &&
            git push origin master

The above snippet won’t work. For readability reasons, I splitted the command on several lines and used some templated string (using back quotes). So, don’t just copy/paste.

Note the || true during the assets commit. It is required in case of the built files have not changed since the last commit. If nothing changed, this line would trigger an error we ignore thanks to the true.

Deploying our website is now as simple as:

npm run deploy

Adding a GitHub pre-push hook may look a better solution at first glance. But it would need to commit built files and push them from the pre-push hook, occuring an infinite recursion. We may handle this case, ensuring we rebuild file only from the outer push, but it would add a lot of complexity. Let’s keep it simple, stupid.

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