webpack.config.js

const path = require('path');
const MiniCssExtractPlugin = require('mini-css-extract-plugin');

module.exports = {
  context: path.resolve(__dirname, 'src'),
  entry: './index.js',
  output: {
    path: __dirname + '/dist',
    filename: './index.js',
    publicPath: '/',
    libraryTarget: 'commonjs2',
  },
  resolve: {
    extensions: ['.js', '.jsx'],
    modules: ['node_modules'],
  },
  optimization: {
    minimize: true,
  },
  module: {
    rules: [
      {
        test: /\.jsx?$/,
        loader: 'babel-loader',
      },
      {
        test: /\.(sass|scss)$/,
        use: [
          {
            loader: MiniCssExtractPlugin.loader,
          },
          {
            loader: require.resolve('css-loader'),
            options: {
              importLoaders: 2,
              modules: {
                mode: 'local',
                localIdentName: '[name]__[local]--[hash:base64:5]',
              },
            },
          },
          'sass-loader',
        ],
      },
    ],
  },
  plugins: [
    new MiniCssExtractPlugin({
      filename: './[name].css',
    }),
  ],
  externals: {
    react: {
      commonjs: 'react',
      commonjs2: 'react',
      amd: 'React',
      root: 'React',
    },
    'react-dom': {
      commonjs: 'react-dom',
      commonjs2: 'react-dom',
      amd: 'ReactDOM',
      root: 'ReactDOM',
    },
  },
};