<html> <body bgcolor="white"> <script language="JavaScript"> function execXMLHttpRequest() { var url = document.getElementById("url").value; var warningElement = document.getElementById("warning"); if (url.indexOf(location.origin) != 0) { warningElement.innerHTML = 'For cross-origin requests to succeed the server must return CORS headers:' + '<pre>Access-Control-Allow-Origin: ' + location.origin + '<br/>Access-Control-Allow-Header: My-Custom-Header</pre>'; warningElement.style.display = 'block'; } else { warningElement.style.display = 'none'; } xhr = new XMLHttpRequest(); xhr.open("GET", url, true); xhr.setRequestHeader('My-Custom-Header', 'Some Value'); xhr.onload = function(e) { if (xhr.readyState === 4) { var value = "Status Code: "+xhr.status; if (xhr.status === 200) value += "\n\n"+xhr.responseText; document.getElementById('ta').value = value; } } xhr.send(); } </script> <form> URL: <input type="text" id="url" value="http://tests/request"> <br/><input type="button" onclick="execXMLHttpRequest();" value="Execute XMLHttpRequest"> <br/><textarea rows="10" cols="40" id="ta"></textarea> </form> <div id="warning" style="display:none;font-weight:bold;"></div> </body> </html>