Middleware & errors

Middleware is registered with use(). A middleware handler receives the context and a next function.

app.use(async (c, next) => {
  const started = performance.now()
  const response = await next()
  const headers = new Headers(response.headers)
  headers.set('x-response-time', `${performance.now() - started}ms`)
  return new Response(response.body, {
    status: response.status,
    statusText: response.statusText,
    headers,
  })
})

Middleware runs before route handlers and can short-circuit by returning a response without calling next().

Before and after hooks

Use before() for application-wide pre-processing and after() for response post-processing:

app.before((c) => {
  c.state.requestId = crypto.randomUUID()
})

app.after((c, response) => {
  const headers = new Headers(response.headers)
  headers.set('x-request-id', c.state.requestId)
  return new Response(response.body, { status: response.status, headers })
})

Hooks can be chained. Route-specific hooks are available with beforeRoute() and afterRoute().

Custom not-found and error handlers

app.notFound((c) => {
  c.status(404)
  return { error: 'not found', path: c.url.pathname }
})

app.onError((error, c) => {
  console.error(error)
  c.status(500)
  return { error: 'internal server error' }
})

HTTPError responses expose their message by default for status codes below 500. Unexpected errors are logged and become a generic 500 response unless an error handler replaces it.

Background work

Use waitUntil() when the runtime supplies an execution context:

import { waitUntil } from 'jinatra'

app.post('/events', async () => {
  waitUntil(writeAuditEvent())
  return { accepted: true }
})