Getting Started

Breakfast integrates modern Javascript tooling into your Rails project.

Get support for ES6 syntax & modules, live reload for CSS, JS, & HTML, and Yarn support. Be up and running on the latest frontend framework in minutes.

As you save your assets they will get compiled on the fly into bundles. Updates get pushed down to the browser and depending on the configured reload strategy will hot swap the code or reload the page automatically.

Powered by Brunch

You can think of Breakfast as the glue between the excellent Brunch build tool and Rails.

Brunch is fundamentally specialized and geared towards building assets, these files that get used in the end by your runtime platform, usually a web browser. It thus comes pre-equipped with a number of behaviors and features. You’ll most notably get:

  • Categorization of source files: JavaScript, Style sheets, Templates and “miscellanea”;
  • Smart concatenation of these files towards one or more target files;
  • Module wrapping of JavaScript files;
  • Handling of front-end dependencies with Yarn;
  • Maintenance of all relevant source maps;
  • Minification of resulting files if we’re in “production mode”;
  • Watching of source files to update the build on the fly.


Breakfast at the moment only supports Rails 5.0+. You will also need Node.js and Yarn installed.


Add breakfast to the Gemfile.

gem "breakfast"

Run bundle install.

To setup Breakfast run the generator that ships with the gem.

rails generate breakfast:install
# Sample Output 
$ rails generate breakfast:install
	create  brunch-config.js
	create  package.json
	create  app/frontend/css
	create  app/frontend/images
	create  app/frontend/js
	create  app/frontend/js/app.js
	create  app/frontend/css/app.scss
	create  app/frontend/images/.gitkeep
		 run  yarn install from "."

Read the linked pages for more information on some of the generated files.


Breakfast out of the box expects the assets in the project to live in the app/frontend/ folder. See the guide for Customizing Asset Location if this does not suit your preference.


Start a Rails server. Almost immediately there should be information in the logs about asset compilation.

info: compiled 6 files into 3 files in 808ms

This first build is combining the JS and CSS into files specified in the brunch-config. By default these will be app.js and app.css.

To get them loaded onto the page use the javascript_include_tag, stylesheet_link_tag and image_tag just like you normally would.

# In application.html.erb

  <%= stylesheet_link_tag "app.css" %>
  <%= javascript_include_tag "app.js" %>
  <%= breakfast_autoreload_tag %>

The breakfast_autoreload_tag setups auto reloading only in development mode.

Understanding Modules

Take a look at the auto generated file app/frontend/js/app.js

const App = {
  init() {

module.exports = App;

Brunch wraps your code in modules, which means that any code that is written is not automatically executed or put into the global state.

The require('frontend/js/app').init() line from above requires the module located at that file path and executes the init function on the returned module.

To see how modules work create another a file app/js/frontend/hello.js.

const HelloWorld = {
  sayHello() {
    console.log("Hello World");

module.exports = HelloWorld;

Modify app.js to import this module and use it.

// Relative Path
import HelloWorld from "./hello"

// Alternative: Full path
// import HelloWorld from "frontend/js/hello"

const App = {
  init() {

module.exports = App;

Note: There are many ways to use imports and exports.

Automatic Processing

On modification of HTML, JS or CSS files output like this should appear in the Rails console.

info: compiled app.scss into app.css in 89ms

Because Brunch is an incremental build system it only rebuilds the bits that change. The first build on server start up was slower because it had to compile everything. As you make changes you’ll find that Brunch does an amazing job at rebuilding particular files in just a few tenths of a second.

Breakfast takes care of running Brunch for you while the Rails server is running. Should you want to run the Brunch build step on your own run:

bin/rails breakfast:assets:build

If you have installed Brunch globally with yarn global add brunch then you can also run:

brunch build

Adding Javascript libraries

Adding Javascript libraries in Rails involves either adding a Gem or downloading a file to vendor/assets/javascripts. To add the library into the application you would use Sprockets require in a manifest file.

With Breakfast you can add frontend libraries using NPM.

For example, to add the Pikaday calender picker run:

yarn add pikaday

This will add the latest version to the package.json and install the code into the node_modules directory. To use the library, return to app/frontend/js/app.js require it.

import Pikaday from "pikaday";

let App = {
  init() {
    let picker = new Pikaday({ field: $('#datepicker')[0] });

module.exports = App;