build.js

const { resolve } = require('path')
const { build, buildSync } = require('esbuild')

const buildWorkerScript = () => {
  const result = buildSync({
    format: 'iife',
    entryPoints: [resolve(__dirname, './src/worker.ts')],
    bundle: true,
    minify: true,
    write: false,
    platform: 'browser',
    loader: {
      '.ts': 'ts',
    },
    tsconfig: resolve(__dirname, './tsconfig.json'),
  })
  return Buffer.from(result.outputFiles[0].contents).toString('utf-8')
}

const run = () => {
  const workerScriptContent = JSON.stringify(buildWorkerScript())

  const formats = {
    cjs: 'index.js',
    esm: 'index.esm.js',
    iife: 'index.iife.js',
  }

  Object.keys(formats).forEach((format) => {
    const fileName = formats[format]
    build({
      format,
      globalName: 'funcWork',
      entryPoints: [resolve(__dirname, './src/index.ts')],
      outfile: resolve(__dirname, './dist/', fileName),
      bundle: true,
      minify: true,
      sourcemap: true,
      platform: 'browser',
      loader: {
        '.ts': 'ts',
      },
      define: {
        __WORKER_SCRIPT__: workerScriptContent,
      },
      tsconfig: resolve(__dirname, './tsconfig.json'),
    }).then(() => {
      console.info(`— ${fileName} was built`)
    }).catch((e) => {
      console.info(`🚨 ${fileName} build error:`)
      console.error(e)
    })
  })
}

run()