vercel-edge-functions

# Vercel Edge Functions ## Overview Edge Functions run on Vercel's Edge Network (V8 isolates) close to the user with no cold starts. They use Web Standard APIs (Request, Response, fetch) instead of Node.js APIs. Ideal for authentication, A/B testing, geolocation routing, and low-latency API responses. ## Prerequisites - Completed `vercel-install-auth` setup - Familiarity with Web APIs (Request/Response) - Node.js 18+ for local development ## Instructions ### Step 1: Create an Edge Function ```typescript // api/edge-hello.ts // Export `runtime = 'edge'` to run on the Edge Runtime export const config = { runtime: 'edge' }; export default function handler(request: Request): Response { return new Response( JSON.stringify({ message: 'Hello from the Edge!', region: request.headers.get('x-vercel-ip-city') ?? 'unknown', timestamp: Date.now(), }), { status: 200, headers: { 'Content-Type': 'application/json' }, } ); } ``` ### Step 2: Edge Function with Geolocation Vercel injects geolocation headers into every edge request: ```typescript // api/geo.ts export const config = { runtime: 'edge' }; export default function handler(request: Request): Response { const city = request.headers.get('x-vercel-ip-city') ?? 'unknown'; const country = request.headers.get('x-vercel-ip-country') ?? 'unknown'; const region = request.headers.get('x-vercel-ip-country-region') ?? 'unknown'; const latitude = request.headers.get('x-vercel-ip-lat...