How do I concatenate and minify files using webpack

Merge multiple CSS into single file can done using extract-text-webpack-plugin or webpack-merge-and-include-globally.

https://code.luasoftware.com/tutorials/webpack/merge-multiple-css-into-single-file/

To merge multiple JavaScripts into single file without AMD or CommonJS wrapper can be done using webpack-merge-and-include-globally. Alternatively, you can expose those wrapped modules as global scope using expose-loader.

https://code.luasoftware.com/tutorials/webpack/merge-multiple-javascript-into-single-file-for-global-scope/

Example using webpack-merge-and-include-globally.

const path = require('path');
const MergeIntoSingleFilePlugin = require('webpack-merge-and-include-globally');

module.exports = {
  entry: './src/index.js',
  output: {
    filename: '[name]',
    path: path.resolve(__dirname, 'dist'),
  },
  plugins: [
    new MergeIntoSingleFilePlugin({
      "bundle.js": [
        path.resolve(__dirname, 'src/util.js'),
        path.resolve(__dirname, 'src/index.js')
      ],
      "bundle.css": [
        path.resolve(__dirname, 'src/css/main.css'),
        path.resolve(__dirname, 'src/css/local.css')
      ]
    })
  ]
};