npm packages are managed by Yarn and any required importing can be done in
yarn build in
package.json. This script also has an entry in
Procfile.dev, so it runs automatically when you start your application with
app/assets/builds directory where it is picked up by the traditional Rails asset pipeline. This directory is listed in
.gitignore, so the compiled bundles are never committed to the repository.
React, Vue.js, etc.