function createRequestObject() { 
   var req; 
   if(window.XMLHttpRequest){ 
      req = new XMLHttpRequest(); 
   } else if(window.ActiveXObject) { 
      req = new ActiveXObject("Microsoft.XMLHTTP"); 
   } else { 
      alert('Problem creating the XMLHttpRequest object'); 
   } 
   return req;
} 
var http = createRequestObject();
function send(wat) {
   http.open('get', 'pagina/signup/check.php?naam='+wat+'&lang='+lang); 
   http.onreadystatechange = Reactie; 
   http.send(null); 
}
function Reactie() { 
   if(http.readyState == 4 && http.status == 200){ 
       document.getElementById('usernamecheck').value = http.responseText;
   } else {
	   document.getElementById('usernamecheck').value = "Loading...";
   }
}