Problem statement is described in this blog post.

1. Install Wrangler.
2. Authenticate with your Cloudflare account using wrangler login.
3. Update wrangler.toml with your event name and webhook key.
4. (Optional) Include allowed origins in the whitelist by updating the index.ts file. Add regular expressions for desired origins to the whitelist array using the format: const whitelist: RegExp[] = [/origin1.com/, /.*\.example\.com/];
5. Deploy the worker using wrangler deploy.

fetch("https://cors-proxy.workers.dev/?apiUrl=https://api.ipify.org?format=json").then(response => {
  return response.json();
}).then(data => {
  console.log(data);
});

where https://api.ipify.org?format=json is the URL you want to fetch and https://cors-proxy.workers.dev is the URL of your deployed worker.