Prototype / Example worker for Cloudflare that pulls from R2

index.js

const corsHeaders = {
    'Access-Control-Allow-Origin': '*',
    'Access-Control-Allow-Methods': 'GET,HEAD,OPTIONS',
    'Access-Control-Max-Age': '86400',
};

async function handleRequest(request) {
    const url = new URL(request.url);
    const key = url.pathname.slice(1);

    const object = await R2.get(key);

    if (object === null) {
      return new Response('Object Not Found', { status: 404 });
    }

    let respHeaders = {
        ...corsHeaders,
        // Allow all future content Request headers to go back to browser
        // such as Authorization (Bearer) or X-Client-Name-Version
        'Access-Control-Allow-Headers': request.headers.get('Access-Control-Request-Headers'),
        'etag': object.httpEtag
      };

    return new Response(object.body, {
        headers: respHeaders,
    });

}

function handleOptions(request) {
    // Make sure the necessary headers are present
    // for this to be a valid pre-flight request
    let headers = request.headers;
    if (
      headers.get('Origin') !== null &&
      headers.get('Access-Control-Request-Method') !== null &&
      headers.get('Access-Control-Request-Headers') !== null
    ) {
      // Handle CORS pre-flight request.
      // If you want to check or reject the requested method + headers
      // you can do that here.
      let respHeaders = {
        ...corsHeaders,
        // Allow all future content Request headers to go back to browser
        // such as Authorization (Bearer) or X-Client-Name-Version
        'Access-Control-Allow-Headers': request.headers.get('Access-Control-Request-Headers'),
      };
  
      return new Response(null, {
        headers: respHeaders,
      });
    } else {
      // Handle standard OPTIONS request.
      // If you want to allow other HTTP Methods, you can do that here.
      return new Response(null, {
        headers: {
          Allow: 'GET, HEAD, OPTIONS',
        },
      });
    }
  }

addEventListener('fetch', event => {
    const request = event.request;
    const url = new URL(request.url);
    if (request.method === 'OPTIONS') {
        // Handle CORS preflight requests
        event.respondWith(handleOptions(request));
    } else if (request.method === 'GET' || request.method === 'HEAD') {
        // Handle requests to the API server
        event.respondWith(handleRequest(request));
    } else {
        event.respondWith(
            new Response(null, {
                status: 405,
                statusText: 'Method Not Allowed',
            })
            );
        }
  });