A sample webpack config file to quickly launch basic projects.

webpack.config.js

//! Webpack configuration file for production mode
// tested with webpack v4.12.0

/**
 * Imports
 */
const autoprefixer = require('autoprefixer');
const webpack = require('webpack');
const CleanWebpackPlugin = require('clean-webpack-plugin');
const ExtractTextPlugin = require('extract-text-webpack-plugin');
const UglifyJsPlugin = require('uglifyjs-webpack-plugin');
const nodeExternals = require('webpack-node-externals');


/**
 * Paths
 */
const path = require('path');
const PATHS = {  
  root: path.resolve(__dirname, './'), // absolute path, project root
  src: path.resolve(__dirname, 'src'),
  dist: path.resolve(__dirname, 'dist'),
  scss: path.resolve(__dirname, 'src', 'scss'),
  js: path.resolve(__dirname, 'src', 'js'),
};

/**
 * Config
 * 
 * ?NOTE: config.mode option set in package.json
 */
const config = {
  //* Context
  // absolute string to the directory that contains the entry files
  context: PATHS.src,

  //* Entry
  // the file webpack looks for to start building the  bundle  
  // If an array is passed all items will be executed.
  // the path is relative to the context dir above
  entry: {
    // relative path declaration
    app: './js/app.js',
    style: './scss/app.scss'
  },

  //* Output
  output: {
    path: PATHS.dist,
    filename: './js/[name].[hash].min.js'
  },

  //* Exclude node_modules from bundle
  // target: 'web', // ignore built-in modules like path, fs, etc.   
  // externals: [nodeExternals()],

  //* Optimization
  // remove “webpackBootstrap” code from bundled output  
  optimization: {
    runtimeChunk: true
  },

  //* Module
  // rules.test    => what should webpack do once a file passes a particular test?
  // rules.use     => process the file using the specified loader 
  // rules.exclude => don't parse using the loader
  module: {
    rules: [
      // babel-loader with 'env' preset
      {
        test: /\.js$/,
        exclude: /node_modules/,
        use: {
          loader: "babel-loader"
        }
      },

      // css-loader, sass-loader
      {
        test: /\.(s*)css$/,
        include: PATHS.scss,
        exclude: ["node_modules"],
        use: ExtractTextPlugin.extract({
          // comment off to prevent bundling of style-loader module
          //fallback: 'style-loader',
          use: [{
              loader: 'css-loader',
              options: {
                minimize: true
              }
            }, // minimize: true => minify css
            {
              loader: 'sass-loader'
            }
          ],
        })
      }
    ]
  },

  //* Plugins
  plugins: [
    // move the css into the output folder
    new ExtractTextPlugin({
      filename: './css/[name].[hash].min.css',
      disable: false,
      allChunks: false
    }),

    // minify javascript
    new UglifyJsPlugin(),

    // empty the output folder before each build
    new CleanWebpackPlugin(['dist']),

    new webpack.LoaderOptionsPlugin({
      options: {
        postcss: [
          autoprefixer()
        ]
      }
    })
  ],

  //* Sourcemaps
  devtool: 'none', // disable sourcemaps
}

/**
 * Exports
 */
module.exports = config;