Code for Cloudflare Worker to be Census API Proxy

census-api-proxy.js

addEventListener("fetch", (event) => {
  event.respondWith(
    handleRequest(event).catch(
      (err) => new Response(err.stack, { status: 500 })
    )
  );
});

 

async function handleRequest(event) {

  let cache = caches.default
  let response = await cache.match(event.request)
    
  if (!response){
    response = await subRequest(event.request)
    if (response.ok) {
      event.waitUntil(cache.put(event.request, response.clone()))
    }
  }
  return response
}

async function subRequest(request) {
  const url = new URL(request.url);
  const params = new URLSearchParams(url.search);
  params.set('key', 'YOUR_API_KEY');
  const sub_response = await fetch(`https://api.census.gov${url.pathname}?${params.toString()}`)
    
  // Recreate the response so we can modify the headers
  const response = new Response(sub_response.body, sub_response)

  // Append to/Add Vary header so browser will cache response correctly
  response.headers.append("Vary", "Origin")
  response.headers.append("Cache-Control", "s-maxage=604800");  
  response.headers.set('cache-control', 'public, max-age=604800')
  response.headers.set("cf-cache-status", "MISS")
  response.headers.delete('set-cookie');  

  return response
}