This Cloudflare Worker proxies and caches requests to a CDN, making it easier to avoid third-party-requests

third-party-cdn-cloudflare-worker-proxy.worker.js

// This Cloudflare Worker proxies and caches requests to a CDN, making it easier to avoid third-party-requests
// https://gist.github.com/hutt/7b3c254a995849e6a06709a872840685/

// Base URL for JSDelivr CDN
const JSDELIVR_BASE_URL = 'https://cdn.jsdelivr.net';

// Path prefix for our proxy
const PROXY_PATH = '/cdn-jsdelivr';

// Default cache duration in seconds (6 hours)
const DEFAULT_CACHE_DURATION = 6 * 60 * 60;

// Listen for incoming fetch events
addEventListener('fetch', event => {
  event.respondWith(handleRequest(event));
});

async function handleRequest(event) {
  try {
    const request = event.request;

    // Parse the request URL
    const url = new URL(request.url);
    
    // Optimized URL processing
    const path = url.pathname;
    if (path.startsWith(PROXY_PATH)) {
      const jsdelivrPath = path.slice(PROXY_PATH.length);
      
      // Construct the full JSDelivr URL
      const jsdelivrUrl = `${JSDELIVR_BASE_URL}${jsdelivrPath}`;
      
      // Try to get the response from cache first
      const cache = caches.default;
      let response = await cache.match(request);

      if (!response) {
        // If not in cache, fetch the resource from JSDelivr
        response = await fetch(jsdelivrUrl, {
          // Forward the original request headers, method, and body
          headers: request.headers,
          method: request.method,
          body: request.body,
        });

        // Clone the response before caching it
        const responseToCache = response.clone();

        // Create new response with custom cache control header
        const newResponse = new Response(responseToCache.body, responseToCache);
        
        // Implement stale-while-revalidate caching
        newResponse.headers.set('Cache-Control', `public, max-age=${DEFAULT_CACHE_DURATION}, stale-while-revalidate=${DEFAULT_CACHE_DURATION}`);
        
        // Set ETag header
        newResponse.headers.set('ETag', response.headers.get('ETag') || crypto.randomUUID());
        
        // Set Content-Encoding header
        newResponse.headers.set('Content-Encoding', response.headers.get('Content-Encoding') || 'gzip');

        // Put the response in cache
        event.waitUntil(cache.put(request, newResponse));
      }

      return response;
    }
    
    // If the path doesn't start with our proxy path, return a 404
    return new Response('Not Found', { status: 404 });
  } catch (error) {
    // Improved error handling
    return new Response(`Error: ${error.message}`, { status: 500 });
  }
}