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# Asset handling with Webpack and Laravel Mix

By default Lucky comes set up with asset handling using Webpack through Laravel Mix. Laravel Mix is a wrapper for common Webpack functionality that makes configuring Webpack much simpler.

# Why Laravel Mix instead of plain Webpack?

Lucky uses Laravel Mix because it is very simple to configure, it’s fast, and it works well for a lot of apps. It is also has methods for configuring webpack as you normally would so you have the full power of Webpack when you need something more complex.

For a lot of people the default Laravel Mix setup will work out of the box, or with little configuration.

Keep in mind that Lucky does not lock you in to using webpack. You can configure other build methods such as Gulp, Grunt, or your own custom at any time.

# Configuring Webpack

There is a webpack.mix.js file in your project root. You can modify this to set up React, change your entry points, etc.

Check out the Laravel Mix documentation for more examples of what you can do.

# Structuring your JavaScript

Babel is set up so you can use new features of JavaScript.

The entry point for JavaScript is src/js/app.js. You’ll see that by default it imports Turbolinks for fast page rendering and RailsUjs to handle AJAX, links with PUT and DELETE requests, and a few other things. Check the Turbolinks and RailsUjs docs for more info.

Note that RailsUjs is required if you are rendering HTML pages in Lucky. If you remove it, PUT and DELETE links will no longer work correctly. You can safely remove Turbolinks without any problems if you don’t want to use it.

To add new JavaScript add files to src/js/{filename} and import them in src/js/app.js

# Structuring your CSS

The main css file is src/css/app.scss and is rendered using SASS. Laravel Mix also sets up autoprefixer so your styles automatically have vendor prefixes.

You can import other files by putting them in src/css/*, and importing them from app.scss. For example, you might put a component in src/css/components/_btn.scss. Remember to end the file with .scss so it’s imported correctly.

Lucky comes with some helpful plugins to make CSS a pleasure to write:

# Removing unwanted packages

Lucky comes with a few JavaScript and CSS packages by default. If you want to remove the ones you don’t want, run yarn remove {package_name}.

If it is a CSS or JavaScript package you may also need to remove the imports from src/css/app.css or src/js/app.js.

# Images, fonts and other assets

You can put images, fonts and other assets in the public/assets folder.

By default there is a public/assets/images folder, but you can add more, such as: fonts, pdfs, etc.

# Background images in CSS

Webpack is set up to ensure your background images are present and fingerprinted. To have Webpack check your background images and make sure they are ready for caching, make sure to use relative URLs:

// Webpack will find the image and rewrite the URL
background: url("../public/assets/images/my-background.jpg")

// Webpack will not do anything special because the path is not relative
background: url("/images/my-background.jpg")

# Loading assets

You can get a path to your assets by using the asset helper in pages.

# Use this in a page or component
# Will find the asset in public/assets/images/logo.png
img src: asset("images/logo.png")

Note that assets are checked at compile time so if it is not found, Lucky will let you know. It will also let you know if you had a typo and suggest an asset that is close to what you typed.

If the path of the asset is only known at runtime, you can use the dynamic_asset helper instead.

img src: dynamic_asset("images/#{name}.png")

# Using assets outside of pages and components

You can use Lucky::AssetHelpers.asset just about anywhere:


# Automatic reloading

Lucky comes with Browsersync hooked up. When you run lucky dev Browsersync will open a tab and automatically reload styles and JavaScript for you. When you change any application files the browser will reload once compilation has been successful.

You can customize Browsersync in the bs-config.js file. You can see a list of options for Browsersync.

# Asset fingerprinting

Fingerprinting means that every asset has a special string of characters appended to the filename so that the browser can cache the file safely. When an asset changes, the fingerprint changes and the browser will use the new version.

Make sure to use the asset macro to get fingerprinted assets.

# Asset compression

Lucky supports static asset compression out of the box with a convenient middleware handler, Lucky::StaticCompressionHandler. You can add to the set of default middleware handlers as necessary in src/

  # ..."./public", file_ext: "br", content_encoding: "br"),"./public", file_ext: "gz", content_encoding: "gzip"),
  # ...

Multiple instances of the StaticCompressionHandler can be leveraged to permit different types of compression based on browser support. For example, the settings above would serve Brotli-compressed assets for browsers that support it, and gzipped assets for those that don’t.

# Asset host

Once your app is in production, you may want to serve up your assets through a CDN. To specify a different host, you’ll use the asset_host option in config/

# In config/
Lucky::Server.configure do |settings|
  if Lucky::Env.production?
    settings.asset_host = ""
    # Serve up assets locally in development and test
    settings.asset_host = ""

# Deploying to production

If you deploy to Heroku, then you won’t need to do anything. Lucky is already set up to build assets in production.

If deploying outside Heroku, make sure to run yarn prod before compiling your project.

See a problem? Have an idea for improvement? Edit this page on GitHub