Cookies

addEventListener("fetch", event => {
  event.respondWith(handleRequest(event.request));
});

async function handleRequest(request) {
  const spCookie = getCookieValue(
    request.headers.get("cookie"),
    "sp-cookie-name"
  );
  const response = await fetch(request);

  // Conditionally add cookie based on presence of sp-cookie-name cookie of request
  if (spCookie) {
    // Using append to add a set-cookie header to response.
    // Use set instead if it is desired to overwrite existing set-cookie headers on response.
    response.headers.append(
      "set-cookie",
      `cookie-name=cookie-value; Domain=.stackpath.com; Path='/';`
    );
  }

  return response;
}

// Taken from https://github.com/pillarjs/cookies/blob/master/index.js#L62
const getCookieValue = (cookies, name) => {
  if (!cookies) {
    return null;
  }
  let regex = new RegExp(
    "(?:^|;) *" + name.replace(/[-[\]{}()*+?.,\\^$|#\s]/g, "\\$&") + "=([^;]*)"
  );
  let match = cookies.match(regex);
  if (!match || !match[1]) {
    return null;
  }
  return match[1];
};