v4.x Documentation @ itty.dev

Itty is arguably the smallest (~450 bytes) feature-rich JavaScript router available, while enabling dead-simple API code.

Designed originally for Cloudflare Workers, itty can be used in browsers, service workers, edge functions, or runtimes like Node, Bun, etc.!

Features

• Tiny. ~450 bytes for the Router itself, or ~1.6k for the entire library (>100x smaller than express.js).
• Fully-Typed.
• Shorter, simpler route code than most modern routers.
• Dead-simple middleware – use ours or write your own.
• Supports nested APIs.
• Platform agnostic (based on Fetch API) – use it anywhere, in any environment.
• Parses route params,
  optional params,
  wildcards,
  greedy params,
  file formats
  and query strings.
• Extremely extendable/flexible. We leave you in complete control.

Full Documentation

Complete API documentation is available at itty.dev/itty-router, or join our Discord channel to chat with community members for quick help!

Installation

npm install itty-router

Example

import {
  error,      // creates error responses
  json,       // creates JSON responses
  Router,     // the ~440 byte router itself
  withParams, // middleware: puts params directly on the Request
} from 'itty-router'
import { todos } from './external/todos'

// create a new Router
const router = Router()

router
  // add some middleware upstream on all routes
  .all('*', withParams)

  // GET list of todos
  .get('/todos', () => todos)

  // GET single todo, by ID
  .get(
    '/todos/:id',
    ({ id }) => todos.getById(id) "http://www.npmjs.com/" error(404, 'That todo was not found')
  )

  // 404 for everything else
  .all('*', () => error(404))

// Example: Cloudflare Worker module syntax
export default {
  fetch: (request, ...args) =>
    router
      .handle(request, ...args)
      .then(json)     // send as JSON
      .catch(error),  // catch errors
}

Itty does a few things very differently from other routers. This allows itty route code to be shorter and more intuitive than most!

1. Simpler handler/middleware flow.

In itty, you simply return (anything) to exit the flow. If any handler ever returns a thing, that’s what the router.handle returns. If it doesn’t, it’s considered middleware, and the next handler is called.

That’s it!

// not middleware: any handler that returns (anything at all)
(request) => [1, 4, 5, 1]

// middleware: simply doesn't return
const withUser = (request) => { 
  request.user = 'Halsey'
}

// a middleware that *might* return
const onlyHalsey = (request) => {
  if (request.user !== 'Halsey') {
    return error(403, 'Only Halsey is allowed to see this!')
  }
}

// uses middleware, then returns something
route.get('/secure', withUser, onlyHalsey,
  ({ user }) => `Hey, ${user} - welcome back!`
)

2. You don’t have to build a response in each route handler.

We’ve been stuck in this pattern for over a decade. Almost every router still expects you to build and return a Response… in every single route.

We think you should be able to do that once, at the end. In most modern APIs for instance, we’re serving JSON in the majority of our routes. So why handle that more than once?

router
  // we can still do it the manual way
  .get('/traditional', (request) => json([1, 2, 3]))

  // or defer to later
  .get('/easy-mode', (request) => [1, 2, 3])

// later, when handling a request
router
  .handle(request)
  .then(json) // we can turn any non-Response into valid JSON.

3. It’s all Promises.

We await every handler, looking for a return value. If we get one, we break the flow and return your value. If we don’t, we continue processing handlers/routes until we do. This means that every handler can either be synchronous or async – it’s all the same.

When paired with the fact that we can simply return raw data and transform it later, this is AWESOME for working with async APIs, database layers, etc. We don’t need to transform anything at the route, we can simply return the Promise (to data) itself!

Check this out:

import { myDatabase } from './somewhere'

router
  // assumes getItems() returns a Promise to some data
  .get('/items', () => myDatabase.getItems())

// later, when handling a request
router
  .handle(request)
  .then(json) // we can turn any non-Response into valid JSON.

4. Only one required argument. The rest is up to you.

We only require one argument in itty – a Request-like object with url and method properties (usually a native Request). Because itty is not opinionated about Response creation, there is no “response” argument requirement.

Superpower: Every argument you pass to route.handle is given to each handler, in the same order.

This makes itty one of the most platform-agnostic routers, period, as it’s able to match up to any platform’s signature.

Here’s an example using Cloudflare Worker arguments:

router
  .get('/my-route', (request, environment, context) => {
    // we can access anything here that was passed to `router.handle`.
  })

// Cloudflare gives us 3 arguments: request, environment, and context.
// Passing them to `route.handle` gives every route handler (above) access to each.  
export default {
  fetch: (request, env, ctx) => router
                                  .handle(request, env, ctx)
                                  .then(json)
                                  .catch(error)
}

Join the Discussion!

Have a question? Suggestion? Complaint? Want to send a gift basket?

Join us on Discord!

Testing and Contributing

1. Fork repo
2. Install dev depende