webpack.config.js

const path = require('path');
const { CleanWebpackPlugin } = require('clean-webpack-plugin');
const HtmlWebpackPlugin = require('html-webpack-plugin');

module.exports = {
  mode: 'production',
  entry: ['./src/js/index.js'],
  output: {
    filename: 'js/index.[hash:8].js',
    path: path.join(__dirname, './build/'),
  },
  devServer: {
    contentBase: './build',
  },
  module: {
    rules: [
      {
        test: /\.jsx?$/,
        exclude: /node_modules/,
        use: {
          loader: 'babel-loader',
        },
      },
      {
        test: /\.js$/,
        include: /node_modules[\\/]@?reactflow/,
        use: {
          loader: 'babel-loader',
          options: {
            presets: ['@babel/preset-env', '@babel/preset-react'],
            plugins: [
              '@babel/plugin-proposal-optional-chaining',
              '@babel/plugin-proposal-nullish-coalescing-operator',
            ],
          },
        },
      },
      {
        // Preprocess 3rd party .css files located in node_modules
        test: /\.css$/,
        include: /node_modules/,
        use: ['style-loader', 'css-loader'],
      },
    ],
  },
  plugins: [
    new CleanWebpackPlugin(),
    new HtmlWebpackPlugin({
      template: path.resolve(__dirname, './src/index.html'),
    }),
  ],
};