webpack.config.js

const path = require('path');
const webpack = require('webpack');
const MiniCssExtractPlugin = require("mini-css-extract-plugin");
const HtmlWebpackPlugin = require('html-webpack-plugin');

const env = process.env.NODE_ENV;

module.exports = {
  entry: './src/index.js',

  mode: env,

  output: {
    path: path.resolve(__dirname, 'dist'),
    filename: '[name].bundle.js',
    publicPath: '/'
  },

  devServer: {
    port: 8000,
  },

  module: {
    rules: [
      {
        test: /\.(js|jsx)$/,
        exclude: /node_modules/,
        use: 'babel-loader'
      },
      {
        test: /\.css$/,
        use: [
          'style-loader',
          'css-loader'
        ]
      }
    ]
  },

  plugins: [
    new HtmlWebpackPlugin({ template: './src/index.html' }),
    new webpack.HotModuleReplacementPlugin(),
    new MiniCssExtractPlugin({
      // Options similar to the same options in webpackOptions.output
      // both options are optional
      filename: "[name].css",
      chunkFilename: "[id].css"
    })
  ]
};