CORS-request test for stadtplan.bonn.de

Demonstration of two servers with only first server allowing CORS-requests.

Expected results as of now:

Request to https://cors-test.appspot.com/test successful.

{"status":"ok"}

Request to https://stadtplan.bonn.de/geojson?Thema=19584&koordsys=25832 unsuccessful.

[object ProgressEvent]

Desired result is that both servers return data and have set the response header:

Access-Control-Allow-Origin: *

<!DOCTYPE html>

<body>
    <script>
        function log(message) {
            $(document.body).append("<p>" + message + "</p>");
        }

// Create the XHR object.
        function createCORSRequest(method, url) {
            var xhr = new XMLHttpRequest();
            // Chrome, Firefox, Safari...
            if ("withCredentials" in xhr) {
                xhr.open(method, url, true);
                // ... IE
            } else if (typeof XDomainRequest != "undefined") {
                xhr = new XDomainRequest();
                xhr.open(method, url);
                // ... some weird browser
            } else {
                xhr = null;
            }
            return xhr;
        }

// Make the actual CORS request.
        function makeCorsRequest(url) {

var xhr = createCORSRequest('GET', url);
            if (!xhr) {
                alert('Browser does not support CORS.');
                return;
            }

// Response handlers.
            xhr.onload = function() {
                log("Request to " + url + " successful.");
                var text = xhr.responseText;
                log(text)
            };

xhr.onerror = function(error) {
                log("Request to " + url + " unsuccessful.");
                log(error)
            };

xhr.send();
        }

// This server allows CORS requests 
        makeCorsRequest('https://cors-test.appspot.com/test')
        // This server disallows CORS requests 
        makeCorsRequest('https://stadtplan.bonn.de/geojson?Thema=19584&koordsys=25832')
    </script>
</body>

https://code.jquery.com/jquery-3.2.1.min.js