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Worker Router

A router for Worker Runtimes such as Cloudflare Workers and Service Workers.

This router is inspired by previous work, specifically tiny-request-router and itty-router, but it improves on them by providing better support for middleware, type inference, nested routing, and broader URL matching for use in service workers.

🆓 Type Inference

The goal of Worker Router is to infer types based on usage so that no explicit typing is required for standard use cases. This allows even JavaScript users to benefit from inline documentation and API discoverability. For example,

const router = new WorkersRouter()
  .get('/about', basics(), (req, { userAgent }) => ok())
  .get('/login', unsignedCookies(), (req, { cookies }) => ok())

In this example your editor can infer the types and documentation for

  • userAgent, provided by the basics middleware
  • cookies, provided by the unsignedCookies middleware

🔋 Functional Middleware

Worker Router middlewares are just function that add properties to a generic context object. As such, they can be mixed and matched using standard tools from functional programming.

For convenience, this module provides a combine utility to combine multiple middlewares into one.

const myReusableMW = combine(
  signedCookies({ secret: 'password123' }), 
  cookieSession({ user: '' })

const router = new WorkersRouter()
  .get('/', myReusableMW, () => ok())
  .post('/', combine(myReusableMW, bodyParser()), () => ok())

Note that type inference is maintained when combining middleware!

🪆 Nested Routing

Worker Router supports delegating entire sub routes to another router:

const itemRouter = new WorkerRouter()
  .get('/', (req, { params }) => ok(`Matched "/item/`))
  .get('/:id', (req, { params }) => ok(`Matched "/item/${}`))

const router = new WorkersRouter()
  .get('/', () => ok('Main Page'))
  .use('/item*', itemRouter)

⚙️ Ready for Service… Worker

Internally, this router uses URLPattern for routing, which allows it match URLs in the broadest sense. For example, the following router, meant to be used in a Service Worker, can handle internal requests as well as intercept calls to external resources:

// file: "sw.js"
const router = new WorkersRouter()
  .get('/', () => ok('Main Page'))
  .get('/about', () => ok('About Page'))
  .external('*', req => {
    // intercepted

💥 Error Handling Without Even Trying

Worker Router has first class support for error handling. Its main purpose is to let you write your handlers without having to wrap everything inside a massive try {} catch block. Instead, you can define special recover routes that get invoked when something goes wrong.

const router = new WorkersRouter()
  .get('/', () => ok('Main Page'))
  .get('/about', () => { throw Error('bang') })
  .recover('*', (req, { error, response }) => 
    new Response(`Something went wrong: ${error.message}`, response)

✅ Works with Workers

Worker Router comes with out of the box support for a variety of Worker Runtimes:

To use it in an environment that provides a global fetch event, use

self.addEventListener('fetch', router)

(This works because the router implements the EventListener interface)

To use it with Cloudflare’s module workers, use

export default router

(This works because the router implements a fetch method with compatible interface)

To use it with Deno/Deploy’s serve function, use


This module is part of the Worker Tools collection

Worker Tools are a collection of TypeScript libraries for writing web servers in Worker Runtimes such as Cloudflare Workers, Deno Deploy and Service Workers in the browser.

If you liked this module, you might also like:

  • 🧭 Worker Router — Complete routing solution that works across CF Workers, Deno and Service Workers
  • 🔋 Worker Middleware — A suite of standalone HTTP server-side middleware with TypeScript support
  • 📄 Worker HTML — HTML templating and streaming response library
  • 📦 Storage Area — Key-value store abstraction across Cloudflare KV, Deno and browsers.
  • 🆗 Response Creators — Factory functions for responses with pre-filled status and status text
  • 🎏 Stream Response — Use async generators to build streaming responses for SSE, etc…
  • 🥏 JSON Fetch — Drop-in replacements for Fetch API classes with first class support for JSON.
  • 🦑 JSON Stream — Streaming JSON parser/stingifier with first class support for web streams.

Worker Tools also includes a number of polyfills that help bridge the gap between Worker Runtimes:

Fore more visit