Edge Functions Cheat Sheet

// app/api/geo/route.tsexport const runtime = 'edge'export async function GET(req: Request) {  const geo = req.headers.get('x-vercel-ip-country') ?? 'unknown'  return new Response(JSON.stringify({ country: geo }), {    headers: { 'content-type': 'application/json' },  })}

export default {  async fetch(request: Request, env: Env, ctx: ExecutionContext): Promise<Response> {    const url = new URL(request.url)    if (url.pathname === '/kv-test') {      const value = await env.MY_KV.get('key1')      return new Response(value ?? 'not found')    }    return new Response('Hello from the edge!')  },}// wrangler.toml// name = "my-worker"// main = "src/index.ts"// compatibility_date = "2026-01-01"// [[kv_namespaces]]// binding = "MY_KV"// id = "..."

Deno.serve(async (req: Request) => {  const { pathname } = new URL(req.url)  if (pathname === '/health') {    return Response.json({ status: 'ok', region: Deno.env.get('DENO_REGION') })  }  return new Response('Not Found', { status: 404 })})// deploy: deployctl deploy --project=my-app main.ts

// middleware.ts (Next.js, runs on the edge by default)import { NextResponse } from 'next/server'import type { NextRequest } from 'next/server'export function middleware(req: NextRequest) {  const token = req.cookies.get('session')?.value  if (!token && req.nextUrl.pathname.startsWith('/dashboard')) {    return NextResponse.redirect(new URL('/login', req.url))  }  return NextResponse.next()}export const config = { matcher: '/dashboard/:path*' }