webpack.common.js

const path = require('path');
const HtmlWebpackPlugin = require('html-webpack-plugin');

module.exports = {
  resolve: {
    // Add '.ts' and '.tsx' as resolvable extensions.
    extensions: ['.ts', '.tsx', '.jsx', '.js'],
    // Modules in ./src should take precedence over those in node_modules
    modules: [path.resolve(__dirname, 'src'), 'node_modules'],
  },

  module: {
    rules: [
      {
        test: /\.ts(x?)$/,
        exclude: /node_modules/,
        use: [
          {
            loader: 'ts-loader',
          },
        ],
      },
      // All output '.js' files will have any sourcemaps re-processed by 'source-map-loader'.
      {
        enforce: 'pre',
        test: /\.js$/,
        loader: 'source-map-loader',
      },
    ],
  },

  plugins: [
    new HtmlWebpackPlugin({
      template: path.resolve(__dirname, 'public/index.html'),
      filename: 'index.html',
    }),
  ],

  output: {
    path: path.resolve(__dirname, './public/js/dist'),
  },

  // When importing a module whose path matches one of the following, just
  // assume a corresponding global variable exists and use that instead.
  // This is important because it allows us to avoid bundling all of our
  // dependencies, which allows browsers to cache those libraries between builds.
  externals: {
    react: 'React',
    'react-dom': 'ReactDOM',
  },

  optimization: {
    usedExports: true,
  },
};