"use strict"; function handleRequest(request, response) { // write to raw socket response.seizePower(); let qs = new URLSearchParams(request.queryString); let imgs = []; let new_hint = true; let new_header = true; for (const [imgUrl, uuid] of qs.entries()) { if (new_hint) { // we need to write a new header new_hint = false; response.write("HTTP/1.1 103 Early Hint\r\n"); } if (!imgUrl.length) { // next hint in new early hint response when empty string is passed new_header = true; if (uuid === "new_response") { new_hint = true; response.write("\r\n"); } else if (uuid === "non_link_header") { response.write("Content-Length: 25\r\n"); } response.write("\r\n"); } else { // either append link in new header or in same header if (new_header) { new_header = false; response.write("Link: "); } else { response.write(", "); } // add query string to make request unique this has the drawback that // the preloaded image can't accept query strings on it's own / or has // to strip the appended "?uuid" from the query string before parsing imgs.push(`

`); response.write(`<${imgUrl}?${uuid}>; rel=preload; as=image`); } } if (!new_hint) { // add separator to main document response.write("\r\n\r\n"); } let body = ` ${imgs.join("\n")} `; // main document response response.write("HTTP/1.1 200 OK\r\n"); response.write("Content-Type: text/html;charset=utf-8\r\n"); response.write("Cache-Control: no-cache\r\n"); response.write(`Content-Length: ${body.length}\r\n`); response.write("\r\n"); response.write(body); response.finish(); }