webpack.config.js

const path = require('path');
const webpack = require('webpack');
const merge = require('webpack-merge');
const CleanWebpackPlugin = require('clean-webpack-plugin');
const MiniCssExtractPlugin = require("mini-css-extract-plugin");
const UglifyJSPlugin = require('uglifyjs-webpack-plugin');

const isProd = process.env.NODE_ENV === 'production';

const common = {
  entry: ['babel-polyfill', './src/index.js'],
  output: {
    path: path.resolve(__dirname, 'public/build'),
    filename: 'script.js',
  },
  module: {
    rules: [
      {
        test: /\.js$/,
        exclude: /node_modules/,
        loader: 'babel-loader',
      },
      {
        test: /\.s?css$/,
        use: [
          'css-hot-loader',
          MiniCssExtractPlugin.loader,
          {
            loader: 'css-loader',
            options: {
              url: false,
              minimize: isProd,
              sourceMap: true,
            },
          },
          {
            loader: 'postcss-loader',
            options: {
              sourceMap: true,
            },
          },
          {
            loader: 'sass-loader',
            options: {
              sourceMap: true,
            },
          },
        ]
      },
    ],
  },
  plugins: [
    new CleanWebpackPlugin(['public/build']),
    new MiniCssExtractPlugin({
      filename: "style.css",
    }),
  ],
};

const configDev = merge(common, {
  mode: 'development',
  devtool: 'inline-source-map',
  devServer: {
    contentBase: path.resolve(__dirname, 'public'),
    publicPath: '/build/',
    hot: true,
    open: true,
    // You can set `host` to your IP to share the development url through network
    // Useful when you want to test on mobile devices or other machines, like windows
    // Example:
    // host: '192.168.1.14',
  },
  plugins: [
    new webpack.NamedModulesPlugin(),
    new webpack.HotModuleReplacementPlugin(),
  ],
});

const configProd = merge(common, {
  mode: 'production',
  devtool: 'source-map',
  plugins: [
    new UglifyJSPlugin({
      sourceMap: true,
    }),
    new webpack.DefinePlugin({
      'process.env.NODE_ENV': JSON.stringify('production'),
    }),
  ],
});

module.exports = (isProd ? configProd : configDev);