webpack.config.js

const path = require("path");
const MonacoWebpackPlugin = require('monaco-editor-webpack-plugin');

module.exports = env => {
  const config = {
    entry: {
        main: "./src/index.tsx",
        worker: "./src/worker.ts"
    },
    output: {
        filename: "[name].bundle.js",
        chunkFilename: "[name].bundle.js",
        path: path.resolve(__dirname, "dist/"),
        publicPath: "/dist/",
    },

    // Enable sourcemaps for debugging webpack's output.
    devtool: "source-map",

    resolve: {
        // Add '.ts' and '.tsx' as resolvable extensions.
        extensions: [".ts", ".tsx", ".js", ".json"]
    },

    module: {
        rules: [
            { test: /\.css$/, use: ['style-loader', 'css-loader'] },

            // All files with a '.ts' or '.tsx' extension will be handled by 'ts-loader'.
            { test: /\.tsx?$/, 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", exclude: path.resolve(__dirname, 'node_modules') }
        ]
    },

    // 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"
    },
    plugins: [
        new MonacoWebpackPlugin()
    ],
    optimization: {
        splitChunks: {
            cacheGroups: {
                editor: {
                    // Editor bundle
                    test: /[\\/]node_modules\/(monaco-editor\/esm\/vs\/(nls\.js|editor|platform|base|basic-languages|language\/(css|html|json|typescript)\/monaco\.contribution\.js)|style-loader\/lib|css-loader\/lib\/css-base\.js)/,
                    name: "monaco-editor",
                    chunks: "async"
                },
                languages: {
                    // Language bundle
                    test: /[\\/]node_modules\/monaco-editor\/esm\/vs\/language\/(css|html|json|typescript)\/(_deps|lib|fillers|languageFeatures\.js|workerManager\.js|tokenization\.js|(tsMode|jsonMode|htmlMode|cssMode)\.js|(tsWorker|jsonWorker|htmlWorker|cssWorker)\.js)/,
                    name: "monaco-languages",
                    chunks: "async"
                }
            }
        }
    }
  };

  return config;
};