More: https://github.com/mahdyar/telemark

telemark-backend.js

addEventListener("fetch", (event) => {
  event.respondWith(handleRequest(event));
});
let data = {
  ok: false,
};
async function handleRequest(event) {
  if (event.request.method == "POST") {
    let body = await event.request.json();
    if (body.url && body.title && body.telemark_code) {
      const url = body.url;
      const title = body.title;
      const telemark_code = body.telemark_code;
      const api =
        "https://api.telegram.org/bot" +
        API_KEY +
        "/sendMessage?chat_id=" +
        telemark_code +
        "&text=[" +
        title +
        "](" +
        url +
        ")&parse_mode=markdown";
      const init = {
        method: "GET",
        headers: {
          "content-type": "application/json;charset=UTF-8",
        },
      };
      const response = await fetch(api, init);
      const responseBody = await response.json();
      data = {
        ok: responseBody.ok,
      };
    }
  }

  const json = JSON.stringify(data, null, 2);
  return new Response(json, {
    headers: {
      "content-type": "application/json;charset=UTF-8",
    },
  });
}