gtm.js

export default {
  async fetch(request, env, ctx) {
    const url = new URL(request.url);

    // Modify the request to point to the Google Tag Manager endpoint
    url.hostname = env.GTM_HOST;

    // Create a new headers object based on the original request headers
    const modifiedHeaders = new Headers(request.headers);

    // Add the geolocation header if available
    if (request.cf && request.cf.regionCode) {
      modifiedHeaders.set('X-CfIpCountryRegion', request.cf.regionCode);
    }

    // Override the Host header to the Google Tag Manager endpoint
    modifiedHeaders.set('Host', env.GTM_HOST);

    // Create a new request with the modified URL and headers
    const modifiedRequest = new Request(url.toString(), {
      ...request,
      headers: modifiedHeaders,
    });

    // Fetch the modified request
    return fetch(modifiedRequest);
  }
};