itty-router

It's an itty bitty router, designed for Express.js-like routing within Cloudflare Workers (or any ServiceWorker). Like... it's super tiny, with zero dependencies. For reals.

Installation

yarn add itty-router

Simple Example

import { Router } from 'itty-router'

// create a router
const router = Router() // this is a Proxy, not a class

// GET index
router.get('/foo', () => new Response('Foo Index!'))

// GET item
router.get('/foo/:id.:format?', request => {
  const { id, format = 'csv' } = request.params

  return new Response(`Getting item ${id} in ${format} format.`)
}

// 404/Missing as final catch-all route
router.all('*', () => new Response('Not Found.', { status: 404 }))

// attach the router handle to the event handler
addEventListener('fetch', event =>
  event.respondWith(router.handle(event.request))
)

Features

• tiny (<450 bytes) with zero dependencies
• route params, with optionals (e.g. /api/:foo/:id?.:format?)
• bonus query parsing (e.g. ?page=3&foo-bar)
• adds params & query to request: { params: { foo: 'bar' }, query: { page: '3' }}
• multiple (sync or async) middleware handlers per route for passthrough logic, auth, errors, etc
• extendable via Proxies
• handler functions "stop" at the first handler to return
• supports nested routers
• supports base path option to prefix all routes
• chainable route declarations (why not?)
• have pretty code (yeah right...)

Options API

Router(options = {})

Name	Type(s)	Description	Examples
base	string	prefixes all routes with this string	Router({ base: '/api' })

Usage

1. Create a Router

import { Router } from 'itty-router'

const router = Router() // no "new", as this is not a real ES6 class/constructor!

2. Register Route(s)

.{methodName}(route:string, handler1:function, handler2:function, ...)

The "instantiated" router translates any attribute (e.g. .get, .post, .patch, .whatever) as a function that binds a "route" (string) to route handlers (functions) on that method type (e.g. router.get --> GET, router.post --> POST). When the url fed to .handle({ url }) matches the route and method, the handlers are fired sequentially. Each is given the original request/context, with any parsed route/query params injected as well. The first handler that returns (anything) will end the chain, allowing early exists from errors, inauthenticated requests, etc. This mechanism allows ANY method to be handled, including completely custom methods (we're very curious how creative individuals will abuse this flexibility!). The only "method" currently off-limits is handle, as that's used for route handling (see below).

Special Exception - the "all" channel: Any routes on the "all" channel will match to ANY method (e.g. GET/POST/whatever), allowing for greater middleware support, nested routers, 404 catches, etc.

// register a route on the "GET" method
router.get('/todos/:user/:item?', (req) => {
  let { params, query, url } = req
  let { user, item } = params

  console.log('GET TODOS from', url, { user, item })
})

3. Handle Incoming Request(s)

.handle(request = { method:string = 'GET', url:string })

The only requirement for the .handle(request) method is an object with a valid full url (e.g. https://example.com/foo). The method property is optional and defaults to GET (which maps to routes registered with router.get()). This method will return the first route handler that actually returns something. For async/middleware examples, please see below.

router.handle({
  method: 'GET',                              // optional, default = 'GET'
  url: 'https://example.com/todos/jane/13',   // required
})

// matched handler from step #2 (above) will execute, with the following output:
// GET TODOS from https://example.com/todos/jane/13 { user: 'jane', item: '13' }

Examples

Nested Routers (with 404 handling)

  // lets save a missing handler
  const missingHandler = new Response('That resource was not found.', { status: 404 })

  // create a parent router
  const parentRouter = Router()

  // and a child router
  const todosRouter = Router({ base: '/todos' })

  // with some routes on it...
  todosRouter
    .get('/', () => new Response('Todos Index'))
    .get('/:id', ({ params }) => new Response(`Todo #${params.id}`))

  // then divert ALL requests to /todos/* into the child router
  parentRouter
    .all('/todos/*', todosRouter.handle) // all /todos/* routes will route through the todosRouter
    .all('*', missingHandler)

  // GET /todos --> Todos Index
  // GET /todos/13 --> Todo #13
  // POST /todos --> missingHandler (it will fail to catch inside todosRouter, and be caught by final "all" on parentRouter)
  // GET /foo --> missingHandler

Middleware

Bonus: Any of these handlers may be awaitable async functions!

// withUser modifies original request, then continues without returning
const withUser = (req) => {
  req.user = { name: 'Mittens', age: 3 }
}

// requireUser optionally returns (early) if user not found on request
const requireUser = (req) => {
  if (!req.user) return new Response('Not Authenticated', { status: 401 })
}

// showUser returns a response with the user, as it is assumed to exist at this point
const showUser = (req) => new Response(JSON.stringify(req.user))

router.get('/pass/user', withUser, requireUser, showUser) // withUser injects user, allowing requireUser to not return/continue
router.get('/fail/user', requireUser, showUser) // requireUser returns early because req.user doesn't exist

router.handle({ url: 'https://example.com/pass/user' }) // --> STATUS 200: { name: 'Mittens', age: 3 }
router.handle({ url: 'https://example.com/fail/user' }) // --> STATUS 401: Not Authenticated

Multi-route (Upstream) Middleware

// withUser modifies original request, then continues without returning
const withUser = (req) => {
  req.user = { name: 'Mittens', age: 3 }
}

router.get('*', withUser) // embeds user before all other matching routes
router.get('/user', (req) => new Response(JSON.stringify(req.user))) // user embedded already!

router.handle({ url: 'https://example.com/user' }) // --> STATUS 200: { name: 'Mittens', age: 3 }

Testing & Contributing

1. fork repo
2. add code
3. run tests (add your own if needed) yarn dev
4. verify tests run once minified yarn verify
5. commit files (do not manually modify version numbers)
6. submit PR
7. we'll add you to the credits :)

The Entire Code (for more legibility, see src on GitHub)

const Router = (o = {}) =>
  new Proxy(o, {
    get: (t, k, c) => k === 'handle'
      ? async (r, ...args) => {
          for ([, p, hs] of t.r.filter(r => r[0] === r.method || 'ALL')) {
            if (m = (u = new URL(r.url)).pathname.match(p)) {
              r.params = m.groups
              r.query = Object.fromEntries(u.searchParams.entries())

              for (h of hs) {
                if ((s = await h(r, ...args)) !== undefined) return s
              }
            }
          }
        }
      : (p, ...hs) =>
          (t.r = t.r || []).push([
            k.toUpperCase(),
            `^${(t.base || '')+p
              .replace(/(\/?)\*/g, '($1.*)?')
              .replace(/\/$/, '')
              .replace(/:([^\/\?\.]+)(\?)?/g, '$2(?<$1>[^/\.]+)$2')
            }\/*$`,
            hs
          ]) && c
  })

Special Thanks

This repo goes out to my past and present colleagues at Arundo - who have brought me such inspiration, fun, and drive over the last couple years. In particular, the absurd brevity of this code is thanks to a clever [abuse] of Proxy, courtesy of the brilliant @mvasigh. This trick allows methods (e.g. "get", "post") to by defined dynamically by the router as they are requested, drastically reducing boilerplate.

Contributors

These folks are the real heroes, making open source the powerhouse that it is! Help us out and add your name to this list!

Core, Concepts, and Codebase

• @hunterloftis - router.handle() method now accepts extra arguments and passed them to route functions
• @roojay520 - TS interface fixes
• @mvasigh - proxy hacks courtesy of this chap

Documentation Fixes

• @arunsathiya