This is the index.js code for a CloudFlare worker to proxy RudderStack's JS SDK and Requests to make them Ad-Blocker Proof

CloudFlare Worker RudderStack Proxy

addEventListener('fetch', event => {
  if(event.request.method === 'OPTIONS'){
    event.respondWith(handleOptions(event.request))
  }else{
    event.respondWith(handleRequest(event.request))
  }
})

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

function handleOptions(request){
  let headers = request.headers;
  if (
    headers.get("Origin") !== null &&
    headers.get("Access-Control-Request-Method") !== null &&
    headers.get("Access-Control-Request-Headers") !== null
  ){
    let respHeaders = {
      ...corsHeaders,
      "Access-Control-Allow-Headers": request.headers.get("Access-Control-Request-Headers"),
    }

    return new Response(null, {headers: respHeaders});
  }else{
    return new Response(null, {headers: {Allow: "GET, HEAD, POST, OPTIONS"}})
  }
}

async function handleRequest(request) {
  const { pathname, origin } = new URL(request.url);
  const DATA_PLANE_URL = 'https://obsessivealnoa.dataplane.rudderstack.com';
  const RUDDER_METHODS = ['page', 'identify', 'group', 'track', 'alias'];
  const RUDDER_SDK_URL = 'https://cdn.rudderlabs.com/v1/rudder-analytics.min.js';
  const RUDDER_SOURCE_CONFIG_URL = 'https://api.rudderlabs.com/sourceConfig';

  if ( pathname === '/sourceConfig/'){
    request = new Request(RUDDER_SOURCE_CONFIG_URL, request)
    request.headers.set("Origin", origin)
    let response = await fetch(request)
    response = new Response(response.body, response);
    response.headers.set("Access-Control-Allow-Origin", '*');
    response.headers.append("Vary", "Origin");
    return response;
  } else if ( pathname === '/dataPlane' ){
    const init = {headers: {'Content-Type': 'application/javascript'}};
    const response = await fetch(RUDDER_SDK_URL, {headers: request.headers});
    const responseText = await response.text();
    return new Response(responseText, init);
  }else{
    const fragments = pathname.split('/');
    /**
     * this is to catch the actual rudder calls which will be in format
     * /v1/page
     * /v1/track
     * etc.
     * Splitting on '/' will give us ['','v1','page'] for instance
     * Rudder request will also be POST requests
     * Time to filter out bad requests
     */
    if (request.method !== 'POST' || !RUDDER_METHODS.includes(fragments[2])){
      return new Response(null, {status: 500});
    }else{
      return fetch(
        `${DATA_PLANE_URL}${pathname}`,
        {
          method: 'POST',
          headers: request.headers,
          body: request.body
        }
      )
    }
  }
}