# cors configuration

        if ($request_method ~* "(GET|POST)") {
          add_header "Access-Control-Allow-Origin"  *;
        }
        # whitelist of allowed domains, via a regular expression
        # if ($http_origin ~* (http://localhost(:[0-9]+)?)) {
         if ($http_origin ~* .*) { # wideopen, for local development. tailor your regex as needed
             set $cors "true";
        }

        # apparently, the following three if statements create a flag for "compound conditions"
        if ($request_method = OPTIONS) {
            set $cors "${cors}options";
        }

        if ($request_method = GET) {
            set $cors "${cors}get";
        }

        if ($request_method = POST) {
            set $cors "${cors}post";
        }

        # now process the flag
        if ($cors = 'trueget') {
            add_header 'Access-Control-Allow-Origin' "$http_origin";
            add_header 'Access-Control-Allow-Credentials' 'true';
        }

        if ($cors = 'truepost') {
            add_header 'Access-Control-Allow-Origin' "$http_origin";
            add_header 'Access-Control-Allow-Credentials' 'true';
        }

        if ($cors = 'trueoptions') {
            add_header 'Access-Control-Allow-Origin' "$http_origin";
            add_header 'Access-Control-Allow-Credentials' 'true';

            add_header 'Access-Control-Max-Age' 120; # cache preflight value in seconds. 300=5 min ; 1728000==20 days
            add_header 'Access-Control-Allow-Methods' 'GET, POST, OPTIONS';
            add_header 'Access-Control-Allow-Headers' 'Authorization,Content-Type,Accept,Origin,User-Agent,DNT,Cache-Control,X-Mx-ReqToken,Keep-Alive,X-Requested-With,If-Modified-Since';
            #add_header 'Access-Control-Allow-Headers' 'Origin, Content-Type, Accept, Authorization, X-Requested-With, Accept-Error, X-CSRF-TOKEN';

            add_header 'Content-Length' 0;
            add_header 'Content-Type' 'text/plain charset=UTF-8';
            return 204;
        }