@kawaz/create-worker

Create Web Workers from inline functions without requiring separate worker files.

Features

• 🎯 Create Workers from inline functions
• 📦 No external dependencies
• 💪 TypeScript support out of the box
• 🔄 Automatic fallback between Data URL and Object URL
• ✨ Type-safe messaging

Installation

npm install @kawaz/create-worker

Basic Usage

import { createWorker } from '@kawaz/create-worker';

// Create a worker from a function
const worker = await createWorker(() => {
  // This is the worker code
  self.onmessage = (e) => {
    const result = e.data * 2;
    self.postMessage(result);
  };
});

// Use the worker
worker.postMessage(21);
worker.onmessage = (e) => {
  console.log(e.data); // Outputs: 42
};

Important Notes

Function Restrictions

The worker function must be self-contained and cannot reference any external variables or closures, as it will be stringified at runtime:

// ❌ Bad - references external variable
const multiplier = 2;
const worker = await createWorker(() => {
  self.postMessage(5 * multiplier); // This will fail. ReferenceError: multiplier is not defined
});

// ✅ Good - all variables are contained within the function
const worker = await createWorker(() => {
  const multiplier = 2;
  self.postMessage(5 * multiplier);
});

Security

• Never pass untrusted functions to createWorker
• Be aware that the function code will be converted to a string
• Consider your Content Security Policy (CSP) settings

CSP Configuration

If your site uses Content Security Policy (CSP), you'll need to add either data: or blob: to the worker-src directive.

Example:

Content-Security-Policy: default-src 'self'; worker-src 'self' data:

API Reference

createWorker

function createWorker(
  workerMain: () => void,
  options?: WorkerOptions
): Promise<Worker>

Parameters

• workerMain: Function to be executed in the worker

  • Must be a self-contained function
  • Cannot reference variables from outer scope
  • Will be stringified at runtime

• options: Standard WorkerOptions object (optional)

  • name: Worker name
  • type: Worker type ('classic' | 'module')
  • Other standard WorkerOptions properties

Returns

Returns a Promise that resolves with a Worker instance.

Throws

• AggregateError: If worker creation fails using both Data URL and Object URL approaches

Development

# Install dependencies
bun install

# Run tests
bun run test

# Build
bun run build

# Lint/Format
bun run lint

Contributing

Contributions are welcome! Please feel free to submit a Pull Request.

1. Fork the repository
2. Create your feature branch (git checkout -b feature/amazing-feature)
3. Commit your changes (git commit -m 'Add some amazing feature')
4. Push to the branch (git push origin feature/amazing-feature)
5. Open a Pull Request

Troubleshooting

Worker Creation Fails

1. Check that your function doesn't reference external variables
2. Verify CSP settings if using in a web application
3. Ensure browser compatibility
4. Check console for detailed error messages

Memory Leaks

• Workers are not automatically terminated
• Call worker.terminate() when done

License

MIT © Yoshiaki Kawazu

Author

Yoshiaki Kawazu

Contributing

Contributions, issues, and feature requests are welcome! Feel free to check issues page.

Support

If you like this project, please consider supporting it by giving a ⭐️ on GitHub!