App - Hono

Hono is the primary object. It will be imported first and used until the end.

import { Hono } from 'hono'

const app = new Hono()
//...

export default app // for Cloudflare Workers or Bun

import { Hono } from 'hono'

const app = new Hono()
//...

export default app // for Cloudflare Workers or Bun

Methods

An instance of Hono has the following methods.

app.HTTP_METHOD([path,]handler|middleware...)
app.all([path,]handler|middleware...)
app.on(method|method[], path, handler|middleware...)
app.use([path,]middleware)
app.route(path, [app])
app.basePath(path)
app.notFound(handler)
app.onError(err, handler)
app.showRoutes()
app.routerName
app.mount(path, anotherApp)
app.fire()
app.fetch(request, env, event)
app.request(path, options)

The first part of them is used for routing, please refer to the routing section.

Not Found

app.notFound allows you to customize a Not Found Response.

app.notFound((c) => {
  return c.text('Custom 404 Message', 404)
})

app.notFound((c) => {
  return c.text('Custom 404 Message', 404)
})

Error Handling

app.onError handles an error and returns a customized Response.

app.onError((err, c) => {
  console.error(`${err}`)
  return c.text('Custom Error Message', 500)
})

app.onError((err, c) => {
  console.error(`${err}`)
  return c.text('Custom Error Message', 500)
})

fire()

app.fire() do this.

addEventListener('fetch', (event) => {
  event.respondWith(this.handleEvent(event))
})

addEventListener('fetch', (event) => {
  event.respondWith(this.handleEvent(event))
})

fetch()

app.fetch will be entry point of your application.

For Cloudflare Workers, you can use the following:

export default {
  fetch(request: Request, env: Env, ctx: ExecutionContext) {
    return app.fetch(request, env, ctx)
  },
}

export default {
  fetch(request: Request, env: Env, ctx: ExecutionContext) {
    return app.fetch(request, env, ctx)
  },
}

or just do:

export default app

export default app

Bun:

export default {
  port: 3000,
  fetch: app.fetch,
}

export default {
  port: 3000,
  fetch: app.fetch,
}

Lagon:

export const handler = app.fetch

export const handler = app.fetch

request()

request is a useful method for testing.

You can pass a URL or pathname to send a GET request. app will return a Response object.

test('GET /hello is ok', async () => {
  const res = await app.request('/hello')
  expect(res.status).toBe(200)
})

test('GET /hello is ok', async () => {
  const res = await app.request('/hello')
  expect(res.status).toBe(200)
})

You can also pass a Request object:

test('POST /message is ok', async () => {
  const req = new Request('Hello!', {
    method: 'POST',
  })
  const res = await app.request(req)
  expect(res.status).toBe(201)
})

test('POST /message is ok', async () => {
  const req = new Request('Hello!', {
    method: 'POST',
  })
  const res = await app.request(req)
  expect(res.status).toBe(201)
})

showRoutes()

app.showRoutes() displays the registered routes in your console.

GET       /v1/posts
GET       /v1/posts/:id
POST      /v1/posts

GET       /v1/posts
GET       /v1/posts/:id
POST      /v1/posts

routerName

You can get the name of the currently used router with app.routerName.

app.get('/', (c) => {
  return c.text(`The current router is ${app.routerName}`)
})

app.get('/', (c) => {
  return c.text(`The current router is ${app.routerName}`)
})

mount()

The mount() allows you to mount applications built with other frameworks into your Hono application.

import { Router as IttyRouter } from 'itty-router'
import { Hono } from 'hono'

// Create itty-router application
const ittyRouter = IttyRouter()

// Handle `GET /itty-router/hello`
ittyRouter.get('/hello', () => new Response('Hello from itty-router'))

// Hono application
const app = new Hono()

// Mount!
app.mount('/itty-router', ittyRouter.handle)

import { Router as IttyRouter } from 'itty-router'
import { Hono } from 'hono'

// Create itty-router application
const ittyRouter = IttyRouter()

// Handle `GET /itty-router/hello`
ittyRouter.get('/hello', () => new Response('Hello from itty-router'))

// Hono application
const app = new Hono()

// Mount!
app.mount('/itty-router', ittyRouter.handle)

strict mode

Strict mode defauls to true and distinguishes the following routes.

/hello
/hello/

app.get('/hello') will not match GET /hello/.

By setting strict mode to false, both paths will be treated equally.

const app = new Hono({ strict: false })

const app = new Hono({ strict: false })

router option

The router option specifices which router to use. The default router is SmartRouter. If you want to use RegExpRouter, pass it to a new Hono instance:

import { RegExpRouter } from 'hono/router/reg-exp-router'

const app = new Hono({ router: new RegExpRouter() })

import { RegExpRouter } from 'hono/router/reg-exp-router'

const app = new Hono({ router: new RegExpRouter() })

Generics

You can pass Generics to specify the types of Cloudflare Workers Bindings and variables used in c.set/c.get.

type Bindings = {
  TOKEN: string
}

type Variables = {
  user: User
}

const app = new Hono<{ Bindings: Bindings; Variables: Variables }>()

app.use('/auth/*', async (c, next) => {
  const token = c.env.TOKEN // token is `string`
  // ...
  c.set('user', user) // user should be `User`
  await next()
})

type Bindings = {
  TOKEN: string
}

type Variables = {
  user: User
}

const app = new Hono<{ Bindings: Bindings; Variables: Variables }>()

app.use('/auth/*', async (c, next) => {
  const token = c.env.TOKEN // token is `string`
  // ...
  c.set('user', user) // user should be `User`
  await next()
})

App - Hono ​

Methods ​

Not Found ​

Error Handling ​

fire() ​

fetch() ​

request() ​

showRoutes() ​

routerName ​

mount() ​

strict mode ​

router option ​

Generics ​