Set security headers

const handler: ExportedHandler = {
  async fetch(request) {
    const DEFAULT_SECURITY_HEADERS = {
      /*
    Secure your application with Content-Security-Policy headers.
    Enabling these headers will permit content from a trusted domain and all its subdomains.
    @see https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Content-Security-Policy
    "Content-Security-Policy": "default-src 'self' example.com *.example.com",
    */
      /*
    You can also set Strict-Transport-Security headers.
    These are not automatically set because your website might get added to Chrome's HSTS preload list.
    Here's the code if you want to apply it:
    "Strict-Transport-Security" : "max-age=63072000; includeSubDomains; preload",
    */
      /*
    Permissions-Policy header provides the ability to allow or deny the use of browser features, such as opting out of FLoC - which you can use below:
    "Permissions-Policy": "interest-cohort=()",
    */
      /*
    X-XSS-Protection header prevents a page from loading if an XSS attack is detected.
    @see https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/X-XSS-Protection
    */
      "X-XSS-Protection": "0",
      /*
    X-Frame-Options header prevents click-jacking attacks.
    @see https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/X-Frame-Options
    */
      "X-Frame-Options": "DENY",
      /*
    X-Content-Type-Options header prevents MIME-sniffing.
    @see https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/X-Content-Type-Options
    */
      "X-Content-Type-Options": "nosniff",
      "Referrer-Policy": "strict-origin-when-cross-origin",
      "Cross-Origin-Embedder-Policy": 'require-corp; report-to="default";',
      "Cross-Origin-Opener-Policy": 'same-site; report-to="default";',
      "Cross-Origin-Resource-Policy": "same-site",
    };
    const BLOCKED_HEADERS = [
      "Public-Key-Pins",
      "X-Powered-By",
      "X-AspNet-Version",
    ];

    let response = await fetch(request);
    let newHeaders = new Headers(response.headers);

    const tlsVersion = request.cf.tlsVersion;
    console.log(tlsVersion);
    // This sets the headers for HTML responses:
    if (
      newHeaders.has("Content-Type") &&
      !newHeaders.get("Content-Type").includes("text/html")
    ) {
      return new Response(response.body, {
        status: response.status,
        statusText: response.statusText,
        headers: newHeaders,
      });
    }

    Object.keys(DEFAULT_SECURITY_HEADERS).map((name) => {
      newHeaders.set(name, DEFAULT_SECURITY_HEADERS[name]);
    });

    BLOCKED_HEADERS.forEach((name) => {
      newHeaders.delete(name);
    });

    if (tlsVersion !== "TLSv1.2" && tlsVersion !== "TLSv1.3") {
      return new Response("You need to use TLS version 1.2 or higher.", {
        status: 400,
      });
    } else {
      return new Response(response.body, {
        status: response.status,
        statusText: response.statusText,
        headers: newHeaders,
      });
    }
  },
};

export default handler;