Webpack
Integrates Drupal with Webpack.
What it does?
The module allows developers to have their Drupal libraries bundled by webpack. It makes it easy to import npm packages and use modern javascript that will work across a variety of browsers (see Webpack Babel).
Dependencies
Right now the module assumes that yarn is installed and available in the PATH.
Setup
Your project needs to have a package.json file somewhere up the directory tree. In drupal-composer projects it is a common practice to place one next to the webroot and the project-wide composer.json. Placing the file inside the webroot would work too. If you don't have such a file, fear not. yarn init -yp will generate an empty one.
Once you've got package.json, add the following npm dependencies.
yarn add webpack
yarn add webpack-serve --dev
Usage
Add webpack: true to your library definition in module_name.libraries.yml.
For local development, start the dev server with yarn webpack:serve and reload the page. The module will detect it and inject the development version (with live reload).
On the server, add yarn webpack:build to your after-deploy steps. The bundles will be written to public://webpack and included automatically.
The output directory can be changed at /admin/config/webpack/settings e.g. to put the files under source control. If you set it to a path that is outside of the public files folder make sure to export your site's config after building (details).
How it works?
Setup steps and the modus operandi have been described in Progressive Decoupling - The why and the how at Decoupled Drupal Days NY 2018.
Should I use it now?
It's still in alpha but the usage won't change much.