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3.0.0 • Public • Published


Dead simple TypeScript bundler, watcher, dev server, transpiler, and polyfiller



The goal of this project is to create a TypeScript bundler that as closely matches the official TypeScript compiler as possible, utilizing as much config from your tsconfig.json as possible, with only minimal additional config required.

This library is basically just a wrapper around webpack with a sensible set of default plugins and configuration for TypeScript projects.

If you later want more customization you should use webpack itself (or another bundler of your choice).


Out of the box tsb offers you:

  • A production build command
  • A development watch command
  • A development serve command
  • Transpiling (with ts-loader)
  • Browser support/polyfilling (with babel)
  • Type checking in a separate thread (with fork-ts-checker-webpack-plugin)
  • Code minification/mangling, offering smaller builds
  • Dead code elimination
  • Expose environment variables and define defaults (with webpack environment plugin)
  • Load environment variables from a .env file (with dotenv)
  • Reference environment variables in your index.html template
  • Hot-loading
  • React hot-loading (with a little extra setup)
  • Bundle hashing
  • Code splitting
  • SPA-style index.html serving and history API fallback

Important things to consider

  • You must set "sourceMap": true in your tsconfig.json to output source maps
  • You must choose an ES module for the tsconfig.json "module" option e.g. "ESNext" (why?)
  • You should include "tsb.config.ts" in your tsconfig.json "include" option to ensure this is type checked (but we'll do that for you during a build anyway)
  • You must install compatible React dependencies to enable React hot-loading


npm i @jakesidsmith/tsb -P

-P is short for --save-prod and will add this to your package.json as a production dependency.


# Bundle TypeScript files (production)
tsb build
# Watch TypeScript files and bundle them when changed (development)
tsb watch
# Run a dev server and update on change (development)
tsb serve


IMPORTANT: read the important things to consider before continuing.

Basic example

Your (minimal) config is defined in a tsb.config.ts e.g.

For a project with the structure:

  # Javascript is output here
import { Config } from '@jakesidsmith/tsb';

const config: Config = {
  main: 'src/index.tsx',
  outDir: 'build',

export default config;

More complex/custom project example

For a more complex project with the following structure:

  # index.html is output here
  # /js/
    # JavaScript is output here
import { Config } from '@jakesidsmith/tsb';

const config: Config = {
  main: 'src/ts/index.tsx',
  outDir: 'build',
  mainOutSubDir: 'js',
  indexHTMLPath: 'src/index.html',
  tsconfigPath: 'src/tsconfig.json',
  publicDir: 'public',
  publicPath: '/public/',

export default config;

And then run this with:

tsb <command> --config src/tsb.config.ts

Environment variables

You must manually specify environment variables that you'd like to include in your bundle. This is a safety precaution to avoid including sensitive information.

These are defined as an object where the keys are the variable names, and the values are default values e.g.

const config: Config = {
  // ...
  env: {
    FALL_BACK_TO_DEFAULT: 'hello',

If any variables are resolved to undefined during a build (both defined as undefined in your config and not exposed by your environment) then the build will error.


By default tsb will look for a tsb.config.ts in the root directory of your project.

You can specify where to look for your config file with the --config CLI option e.g.

tsb build --config custom/location/tsb.config.ts

By default tsb will look for a tsconfig.json in the root of your project, but you can override this with the tsconfigPath option in your tsb.config.ts.

All config options

interface Config {
  // Required
  // Path to your TypeScript/JavaScript entry point
  main: string;
  // Path to the directory to output files
  outDir: string;
  // Base options
  // List of commands for which the outDir should be cleared before
  clearOutDirBefore?: readonly ('build' | 'watch' | 'serve')[]; // Default: []
  // Sub-directory to output JavaScript files within `outDir`
  mainOutSubDir?: string;
  // Name for the main bundle output
  mainBundleName?: string; // Default: 'bundle'
  // Path to tsconfig.json
  tsconfigPath?: string; // Default: tsconfig.json in the root of the project
  // Path to a custom index.html template
  indexHTMLPath?: string;
  // Variables to expose to the index.html template (referenced with <%= example %>)
  indexHTMLEnv?: Record<string, any>;
  // List of commands for which to output index.html to disk
  outputIndexHTMLFor?: readonly ('build' | 'watch' | 'serve')[]; // Default: ['build', 'watch']
  // Whether to add script tag to body, head, or not at all
  insertScriptTag?: 'body' | 'head' | false; // Default: 'body'
  // Whether add "defer" attribute to script tag.
  scriptLoading?: 'blocking' | 'defer' | 'module'; // default 'blocking'
  // Whether React hot-loading is enabled
  reactHotLoading?: boolean; // Default: false
  // List of commands for which output bundles are hashed
  hashFilesFor?: readonly ('build' | 'watch' | 'serve')[]; // Default: ['build', 'watch']
  // List of paths/globs to files outside of your tsconfig.json includes that should be parsed
  additionalFilesToParse?: readonly string[];
  // Map of environment variables to include (key: variable name, value: default value (set undefined if  don't want a default))
  env?: Record<string, any>;
  // Dev server options
  // Whether hot-loading is enabled
  hotLoading?: boolean; // Default: true
  // Host of the dev server (e.g. '' or 'localhost')
  host?: string; // Default: ''
  // Port to run the dev server on
  port?: number; // Default: 8080
  // Path to the directory in which additional public/static files should be served from
  publicDir?: string;
  // Public path to refer to files stored in the `publicDir`
  publicPath?: string;
  // Whether to enable SPA-style index.html serving and history API fallback
  singlePageApp?: boolean; // Default: true
  // Custom headers to send with dev server requests
  headers?: Record<string, string>;
  // Whether to enable https (self signed certificate)
  https?: boolean;
  // Extend the babel presets
  extendBabelPresets?: (
    presets: BabelPluginItem[],
    mode: Mode,
    command: Command
  ) => BabelPluginItem[];
  // Extend the babel plugins
  extendBabelPlugins?: (
    plugins: BabelPluginItem[],
    mode: Mode,
    command: Command
  ) => BabelPluginItem[];
  // Extend the webpack plugins
  extendWebpackPlugins?: (
    plugins: WebpackPlugin[],
    mode: Mode,
    command: Command
  ) => WebpackPlugin[];
  // Extend the webpack module.rules
  extendWebpackModuleRules?: (
    rules: WebpackModuleRule[],
    mode: Mode,
    command: Command
  ) => WebpackModuleRule[];

Code splitting

In order to split your bundle, you should use dynamic imports at the locations where you'd like the modules to be split.

You can name the output bundles by supplying a comment e.g.

import(/* webpackChunkName: "my-file" */ './path/to/file');

You can also set chunks to be pre-loaded.

More info here: https://webpack.js.org/guides/code-splitting/

React hot-loading

React hot-loading is disabled by default. To enable this set the reactHotLoading option to true.

In order for hot-loading to work correctly you must install react-hot-loader, and matching versions of the relevant react libraries - react, react-dom, and @hot-loader/react-dom e.g.

npm i react@17 react-dom@17 -P
# These are only needed in development so we'll use -D to add them as dev dependencies
npm i @hot-loader/react-dom@17 react-hot-loader -D

You will also need to mark your root component as hot-exported:

import { hot } from 'react-hot-loader/root';

const App = () => <div>Hello World!</div>;

export default hot(App);

More info here: https://github.com/gaearon/react-hot-loader

React hot-loading is currently implemented with react-hot-loader and only supports React <= 16. If you want to support React 17 you can use the experimental @pmmmwh/react-refresh-webpack-plugin with the extendBabelPlugins and extendWebpackPlugins options. You should not enable reactHotLoading if you are using react-refresh.

Example with react-refresh:

import ReactRefreshWebpackPlugin from '@pmmmwh/react-refresh-webpack-plugin';

const config: Config = {
  // ...base config...
  reactHotLoading: false,
  extendBabelPlugins: (plugins, mode, command) => {
    if (command === 'serve') {
      return [...plugins, require.resolve('react-refresh/babel')];

    return plugins;
  extendWebpackPlugins: (plugins, mode, command) => {
    if (command === 'serve') {
      return [...plugins, new ReactRefreshWebpackPlugin()];

    return plugins;

Dev server

By default the dev server will create an index.html file for you and serve this.

If you have a custom index.html file, or need this to be processed by another templating engine you can specify a location for this in the indexHTMLPath config option.

Why ES modules?

You must choose an ES module for the tsconfig.json "module" option e.g. "ESNext".

This is to improve build performance and better handle dead code elimination.

Don't worry, we'll still output browser friendly bundles that use CommonJS.

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