Make sure you have NodeJS 8.x or higher.

Then, modules needed for the Roon API and for the dev tools:

npm install

To build for deployment:

npm run build

This will generate a bundle.js from your app.js and everything else. You include this bundle.js in your browser.

To build for dev purposes:

npm run dev

This will watch your js and html and update the bundle.js immediately on changes.