How to minifiy webpack codes in Rails 6

First install uglifyjs-webpack-plugin with yarn

yarn add uglifyjs-webpack-plugin

Then add these line in webpack configeriation file

// config/webpack/production.js
const UglifyJsPlugin = require('uglifyjs-webpack-plugin')

environment.config.set('optimization.minimizer', [new UglifyJsPlugin()])

It's done!

Reference

• https://github.com/rails/webpacker/blob/master/docs/webpack.md
• https://webpack.js.org/plugins/uglifyjs-webpack-plugin/#getting-started