This is an example Rails 5.1 app with Elm on the front-end handled by Webpacker, running on Heroku.
To deploy to Heroku, create a Heroku app, configure the buildpacks and push:
$ heroku git:remote -a <Heroku app name>
$ heroku buildpacks:add heroku/nodejs
$ heroku buildpacks:add heroku/ruby
$ git push heroku master
$ bundle
$ yarn install
$ foreman start
Now you can visit localhost:5000
from your browser.