Middleware

Middleware functions are used to run custom logic before or after the main request handler. They can modify the request, add headers to the response, handle errors, perform authentication, logging, validation, and more. Middleware in backan is registered using app.use() and can be applied globally or scoped to specific routes.

Usage

import { App } from 'backan'
const app = new App( )

app.use('*', async ( c, next ) => {

  const start = Date.now()
  await next()
  const end = Date.now()
  c.res.headers.set('X-Response-Time', `${end - start}`)

} )

Examples

🔍 Simple Logger

import { App } from 'backan'
const app = new App()

app.use('*', async (c, next) => {
  console.log(`[${new Date().toISOString()}] ${c.req.method} ${c.req.url}`)
  await next()
})

🔐 Basic Authentication

app.use('/admin/*', async (c, next) => {
  const token = c.req.header('authorization')
  if (token !== 'Bearer supersecrettoken') {
    return c.text('Unauthorized', 401)
  }
  await next()
})

📦 Enforce JSON Content-Type

app.use('/api/*', async (c, next) => {
  if (c.req.header('content-type') !== 'application/json') {
    return c.json({ error: 'Only JSON requests are allowed' }, 415)
  }
  await next()
})

🧠 Add Data to Context

app.use('/profile', async (c, next) => {
  c.set('userId', '1234') // example: add user ID
  await next()
})

app.get('/profile', (c) => {
  const userId = c.get('userId')
  return c.json({ userId })
})

🛑 Global Error Handler

app.use('*', async (c, next) => {
  try {
    await next()
  } catch (err) {
    console.error('Unhandled error:', err)
    return c.json({ error: 'Internal Server Error' }, 500)
  }
})

---

📊 Response Time Header

app.use('*', async (c, next) => {
  const start = performance.now()
  await next()
  const end = performance.now()
  c.res.headers.set('X-Response-Time', `${end - start}ms`)
})