Method headers

packages/engine.io/lib/transports/polling.ts:383–395

* Returns headers for a response. * * @param {http.IncomingMessage} req * @param {Object} headers - extra headers * @private

(req: IncomingMessage, headers: Record<string, string> = {})

   * @private
   */
  private headers(req: IncomingMessage, headers: Record<string, string> = {}) {
    // prevent XSS warnings on IE
    // https://github.com/LearnBoost/socket.io/pull/1333
    const ua = req.headers["user-agent"];
    if (ua && (~ua.indexOf(";MSIE") || ~ua.indexOf("Trident/"))) {
      headers["X-XSS-Protection"] = "0";
    }

    headers["cache-control"] = "no-store";

    this.emit("headers", headers, req);
    return headers;
  }
}