@jakesidsmith/tsb/src/commands/watch.ts

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

import webpack from 'webpack';
import { createWebpackConfig } from '../webpack-config';
import { createWebpackCallback } from '../webpack-callback';

const build = (configPath: string | undefined): void => {
  const webpackConfig = createWebpackConfig(configPath, 'development', 'watch');
  const callback = createWebpackCallback(false);

  webpack(webpackConfig.base).watch({}, callback);
};

export default build;