Based on the fact that the request isn't sent on the default port 80/443 this Ajax call is automatically considered a cross-origin resource (CORS) request, which in other words means that the request automatically issues an OPTIONS request which checks for CORS headers on the server's/servlet's side.
This happens even if you set
crossOrigin: false;
or even if you ommit it.
The reason is simply that localhost != localhost:57124
. Try sending it only to localhost
without the port - it will fail, because the requested target won't be reachable, however notice that if the domain names are equal the request is sent without the OPTIONS request before POST.