Cloudflare Worker JS code to cache Wordpress HTML for logged-out users.

cloudflare_worker.js

/*I make no guarantees this code will work reliably. Use at your own risk. Please thoroughly test before deploying.

Enabling this on a Cloudflare Worker for a Wordpress site should cache all HTML pages (if your origin headers allow that) but bypass the cache when a user is logged in.
This is tested and working on a Wordpress 5.0.2 installation and the free Cloudflare tier (but I make no guarentees it will work for anyone else).

Sets the `x-cfw-cache` header to indicate the Worker cache status (either HIT, MISS, NO, or BYPASS): `NO` = server has set cookies (won't cache) and `BYPASS` = client has cookies (bypassing cache).
*/

addEventListener('fetch', event => {
  event.respondWith(handleRequest(event))
})

async function handleRequest(event) {
  let request = event.request;
  let response = null;
  cookies = request.headers.get("Cookie");
  if (cookies && cookies.toLowerCase().includes("wordpress_")){
    console.log("We have cookies. Don't cache.", cookies);
    response = await fetch(request);
    response = new Response(response.body, response);
    response.headers.set("x-cfw-cache", "BYPASS");
    return response;
  }
  let cache = caches.default;
  response = await cache.match(request);
  if (response && response.status !== 200){
    response = null;
  }
  if (!response){
    console.log("No cache. Will fetch.");
    response = await fetch(request);
    response = new Response(response.body, response);
    let responsecookies = response.headers.get("Set-Cookie");
    if (responsecookies && responsecookies.toLowerCase().includes("wordpress_")){
      //Wordpress auth/test cookies are being set here. We don't want to cache.
      response.headers.set("x-cfw-cache", "NO");
    } else {
      
      response.headers.delete("Set-Cookie"); //Cloudflare won't cache responses containing Set-Cookie.
      response.headers.set("x-cfw-cache", "MISS");
      if (response.status == 200){
        event.waitUntil(cache.put(request, response.clone()));
      }
    }
  } else {
    response = new Response(response.body, response);
    response.headers.set("x-cfw-cache", "HIT");
  }
  
  return response
}