A simple Cloudflare Worker that demonstrates using HTMLRewriter to change 3rd party site (Polywork page)

cf-worker-polywork-proxy.js

// This script is running on https://eidam.dev
// change dnsWithPolyworkCustomDomainCname to your CNAME record set to provided record by Polywork
// note: you cannot use Polywork record directly
const dnsWithPolyworkCustomDomainCname = "polywork-origin.eidam.dev"

// change link to your list of links
const links = [
    {link: "https://github.com/eidam", name: "🍴 https://github.com/eidam"},
    {link: "https://twitter.com/adam_janis", name: "🐤 https://twitter.com/adam_janis"},
    {link: "https://statusflare.com", name: "📈 https://statusflare.com"},
]

addEventListener("fetch", (event) => {
  event.respondWith(
    handleRequest(event.request).catch(
      (err) => new Response(err.stack, { status: 500 })
    )
  );
});

/**
 * @param {Request} request
 * @returns {Promise<Response>}
 */
async function handleRequest(request) {
  const { pathname } = new URL(request.url)
  
  // fetch Polywork HTML
  let res = await fetch(request, {
      // resolve override to custom domain CNAME
      // and cache Polywork response for 2 hours
      cf: {
          resolveOverride: dnsWithPolyworkCustomDomainCname,
          cacheTtl: 3600 * 2,
      }
  })

  // run HTMLRewriter for index responses
  // and replace introduction block with custom list
  // or return cached Polywork response for the rest of pages
  return pathname == "/" ? 
    new HTMLRewriter()
        .on("#profile-introduction-panel .text-size-introduction", {
        element(element) {
            element.replace(`
              <div class="text-muted text-size-introduction">
                <ul>
                    ${links.map(link => {
                        return `<li><a href="${link.link}" target="_blank" rel="noopener">${link.name}</a></li>`
                    }).join("\n")}
                </ul>
                <a href="/eidam/expanded">
                    <h5 class="d-inline text-dark">Read more</h5>
                </a>
              </div>
            `, {html: true})
            },
        })
        .transform(res)
    : res
}