Context Object

The Context object wraps the native Request and provides convenient methods for accessing request data, setting response headers, and sending responses.

What is Context?

Context is a wrapper around Deno's native Request object. Instead of working with raw Request directly, you use Context which gives you:

• Lazy parsing - Data is parsed only when you access it
• Convenient methods - Simple APIs for common operations
• Response utilities - Built-in methods for sending responses
• Header management - Easy response header manipulation

Why Using Context?

Context avoids multiple parsing and repeated processing during the request lifecycle. The handler receives one Context object that persists through the entire lifecycle — from middleware to route handler.

Creating Context

Deserve creates Context automatically when requests arrive:

import type { Context } from '@neabyte/deserve'

export function GET(ctx: Context): Response {
  return ctx.send.json({ message: 'Hello' })
}

Context Structure

Context wraps several key pieces:

1. Original Request - Access via ctx.request
2. Parsed URL - Used internally for query params
3. Route Parameters - Extracted from dynamic routes
4. Response Headers - Set before sending response

Lazy Parsing

Context uses lazy parsing for performance:

export function GET(ctx: Context): Response {
  // Query params aren't parsed yet

  const query = ctx.query() // Parsed on first access
  // Now cached, subsequent calls return cached value

  const body = await ctx.body() // Parsed on first access
  // Parsed based on Content-Type

  return ctx.send.json({ query, body })
}

Request Data Access

Access request data through Context methods:

• Query Parameters - ctx.query(), ctx.queries()
• Route Parameters - ctx.param(), ctx.params()
• Headers - ctx.header(), ctx.headers
• Cookies - ctx.cookie()
• Body - ctx.body(), ctx.json(), ctx.formData(), ctx.text(), ctx.arrayBuffer(), ctx.blob()
• URL Information - ctx.url, ctx.pathname

Response Utilities

Send responses using ctx.send:

• ctx.send.json() - JSON responses
• ctx.send.text() - Plain text
• ctx.send.html() - HTML content
• ctx.send.file() - File downloads
• ctx.send.data() - In-memory data downloads
• ctx.send.redirect() - Redirects
• ctx.send.custom() - Custom responses
• ctx.handleError() - Error handling

You can also use ctx.redirect() directly as a convenience method:

export function GET(ctx: Context): Response {
  return ctx.redirect('/new-location', 301)
  // Equivalent to: ctx.send.redirect('/new-location', 301)
}

Response Headers

Set response headers before sending:

export function GET(ctx: Context): Response {
  ctx.setHeader('X-Custom', 'value')
  ctx.setHeader('Cache-Control', 'no-cache')
  return ctx.send.json({ data: 'test' })
}

Setting Multiple Headers

Use setHeaders() to set multiple headers at once:

export function GET(ctx: Context): Response {
  ctx.setHeaders({
    'X-Custom': 'value',
    'Cache-Control': 'no-cache',
    'X-Request-ID': 'abc123'
  })
  return ctx.send.json({ data: 'test' })
}

Reading Response Headers

Access all response headers that have been set:

export function GET(ctx: Context): Response {
  ctx.setHeader('X-Custom', 'value')
  ctx.setHeader('Cache-Control', 'no-cache')
  const headers = ctx.responseHeadersMap // { 'X-Custom': 'value', 'Cache-Control': 'no-cache' }
  return ctx.send.json({ data: 'test' })
}

URL and Pathname

Get URL information directly:

• ctx.url - Full URL string
• ctx.pathname - Pathname portion of URL (e.g., /api/users/123)

export function GET(ctx: Context): Response {
  const fullUrl = ctx.url // 'http://localhost:8000/api/users/123?sort=name'
  const path = ctx.pathname // '/api/users/123'
  return ctx.send.json({ path, fullUrl })
}

Error Handling

Handle errors consistently using ctx.handleError():

export function GET(ctx: Context): Response {
  try {
    if (!isAuthorized) {
      return ctx.handleError(401, new Error('Unauthorized'))
    }
    return ctx.send.json({ data: 'success' })
  } catch (error) {
    return ctx.handleError(500, error as Error)
  }
}

How It Works

ctx.handleError() respects your global error handler set with router.catch():

• If router.catch() is defined - Uses your custom error handler
• If no error handler - Returns a simple response with the status code

Use in Middleware

Middleware can use ctx.handleError() to trigger error handling:

router.use(async (ctx, next) => {
  if (!isValid) {
    return ctx.handleError(401, new Error('Unauthorized'))
    // This will use router.catch() if defined
  }
  return await next()
})

Context Lifecycle

1. Request arrives - Deserve creates Context with Request and URL
2. Route matching - Route parameters extracted and added to Context
3. Middleware execution - Context passed through middleware chain
4. Route handler - Your handler receives Context
5. Response sent - Context methods used to build Response