h3

Tiny JavaScript Server

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H3 is a minimal h(ttp) framework built for high performance and portability

Features

✔️  Portable: Works perfectly in Serverless, Workers, and Node.js

✔️  Compatible: Support connect/express middleware

✔️  Minimal: Small, tree-shakable and zero-dependency

✔️  Modern: Native promise support

✔️  Extendable: Ships with a set of composable utilities but can be extended

✔️  Router: Super fast route matching using unjs/radix3

Install

# Using npm
npm install h3

# Using yarn
yarn add h3

# Using pnpm
pnpm add h3

Usage

import { createServer } from 'http'
import { createApp } from 'h3'

const app = createApp()
app.use('/', () => 'Hello world!')

createServer(app).listen(process.env.PORT || 3000)
Example using listhen for an elegant listener.
import { createApp } from 'h3'
import { listen } from 'listhen'

const app = createApp()
app.use('/', () => 'Hello world!')

listen(app)

Router

The app instance created by h3 uses a middleware stack (see how it works) with the ability to match route prefix and apply matched middleware.

To opt-in using a more advanced and convenient routing system, we can create a router instance and register it to app instance.

import { createApp, createRouter } from 'h3'

const app = createApp()

const router = createRouter()
 .get('/', () => 'Hello World!')
 .get('/hello/:name', req => `Hello ${req.context.params.name}!`)

app.use(router)

Tip: We can register same route more than once with different methods.

Routes are internally stored in a Radix Tree and matched using unjs/radix3.

More usage examples

// Handle can directly return object or Promise<object> for JSON response
app.use('/api', (req) => ({ url: req.url }))

// We can have better matching other than quick prefix match
app.use('/odd', () => 'Is odd!', { match: url => url.substr(1) % 2 })

// Handle can directly return string for HTML response
app.use(() => '<h1>Hello world!</h1>')

// We can chain calls to .use()
app.use('/1', () => '<h1>Hello world!</h1>')
   .use('/2', () => '<h1>Goodbye!</h1>')

// Legacy middleware with 3rd argument are automatically promisified
app.use((req, res, next) => { req.setHeader('X-Foo', 'bar'); next() })

// Force promisify a legacy middleware
// app.use(someMiddleware, { promisify: true })

// Lazy loaded routes using { lazy: true }
// app.use('/big', () => import('./big'), { lazy: true })

Utilities

Built-in

Instead of adding helpers to req and res, h3 exposes them as composable utilities.

  • useRawBody(req, encoding?)
  • useBody(req)
  • useCookies(req)
  • useCookie(req, name)
  • setCookie(res, name, value, opts?)
  • deleteCookie(res, name, opts?)
  • useQuery(req)
  • getRouterParams(event)
  • send(res, data, type?)
  • sendRedirect(res, location, code=302)
  • getRequestHeaders(event, headers) (alias: getHeaders)
  • getRequestHeader(event, name) (alias: getHeader)
  • setResponseHeaders(event, headers) (alias: setHeaders)
  • setResponseHeader(event, name, value) (alias: setHeader)
  • appendResponseHeaders(event, headers) (alias: appendHeaders)
  • appendResponseHeader(event, name, value) (alias: appendHeader)
  • createError({ statusCode, statusMessage, data? })
  • sendError(res, error, debug?)
  • defineHandle(handle)
  • defineMiddleware(middlware)
  • useMethod(req, default?)
  • isMethod(req, expected, allowHead?)
  • assertMethod(req, expected, allowHead?)

👉 You can learn more about usage in JSDocs Documentation.

Add-ons

More composable utilities can be found in community packages.

How it works?

Using createApp, it returns a standard (req, res) handler function and internally an array called middleware stack. usinguse() method we can add an item to this internal stack.

When a request comes, each stack item that matches the route will be called and resolved until res.writableEnded flag is set, which means the response is sent. If writableEnded is not set after all middleware, a 404 error will be thrown. And if one of the stack items resolves to a value, it will be serialized and sent as response as a shorthand method to sending responses.

For maximum compatibility with connect/express middleware (req, res, next? signature), h3 converts classic middleware into a promisified version ready to use with stack runner:

  • If middleware has 3rd next/callback param, the promise will resolve/reject when called
  • If middleware returns a promise, it will be chained to the main promise
  • If calling middleware throws an immediate error, the promise will be rejected
  • On close and error events of res, the promise will resolve/reject (to ensure if middleware simply calls res.end)

License

MIT