Basic Cloudflare Worker that allows efficient page caching for Wordpress websites

cf-wp-cache-worker.js

// Version 1.4
const DAY_IN_SECONDS = 60*60*24;

const BLACKLISTED_URL_PARAMS = [ 
  'fbclid',                     // Google Ads click Id
  'gclid',                      // Facebook click Id
  'msclkid',                    // Micorosft Ads Click Id
];

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

async function fetchAndApply(request) {
  
  let cloudflareOptions = {}

  let url = new URL(request.url)

  // Bypass Cache if is a non cachable WP request or is not a GET request
  let bypassCache = isWordpressNoCache( request ) || (request.method !== 'GET');

  if ( bypassCache  ) {
    // Disable page Cache, this shoud keep the static assets cache on.
    cloudflareOptions.cacheEverything = false;
  } else {    
    // Force request caching 
    cloudflareOptions.cacheEverything = true;

    // Set Edge Cache default TTL
    cloudflareOptions.cacheTtl = 365 * DAY_IN_SECONDS;

    // Set thje edge cache TTL by response status
    cloudflareOptions.cacheTtlByStatus = { 
      "200-299": 365 * DAY_IN_SECONDS, 
      404: 60 * DAY_IN_SECONDS, 
      "500-599": 100
    };
    
    //blacklisted url params
    BLACKLISTED_URL_PARAMS.forEach((blParam) => {
      url.searchParams.delete(blParam);
    });

    //or delete all URL parameters unconditionally
    //url.search = '';
  }

  //create a new editable request
  let newRequest = new Request(url.toString(), request );

  // Pipe the request to the CF servers and wait for the response
  let response = await fetch(newRequest, {cf : cloudflareOptions} );

  // Copy the response so that we can modify headers.
  response = new Response(response.body, response)

  // Lower the browser max-age for pages to 1 mins. This is done to avoid caching a website page
  // on user device for the entire edge cache TTL (default CF behavior). We can't purge or invalidate it!
  if ( !bypassCache && !isStaticFile( response ) ) {
    response.headers.set("Cache-Control", "max-age=60");
  }

  // return the response to client
  return response
}

// Checks if we should not cache the request due to one of the following reasons:
//  * user logged in
//  * user is commenting a post
//  * user has some products in cart or is using woocommerce
//  * user is in the wp-admin section or other WP related resources
function isWordpressNoCache( request ) {
  
  // Get full URL from the request
  const url = new URL(request.url)

  // Get raw cookies from the request
  const cookie = request.headers.get('Cookie');

  //Create a regex to match cookies that suggeest: user logged-in, comments or woocomerce session
  const wpRegex = /;\s?(wordpress_logged_in_|comment_|woocommerce_)[^=]+=/g;

  return (
       // If request contains cookies check if there are WP related cookies
       ( cookie && cookie.match(wpRegex) )
       // Check if the URL path is WP Core related
       || url.pathname.startsWith('/wp-')
       // Check if the URL path is WP Core related (roots/bedrock version)
       || url.pathname.startsWith('/wp/wp-') );
    
}

// Check if a response is a static file or a document or API response
function isStaticFile( response ){
  // Get content-type from the response
  let contentType = response.headers.get('content-type');

  // Check if the response content type is an HTML page or a JSON object
  if ( contentType && ( contentType.startsWith('text/html') || contentType.startsWith('application/json') ) ) {
    return false;
  }

  return true;
}