Simple Ajax/SuiteLet Example

I've create what I think is the simplest call to a SuiteLet. However, the Ajax return value is consistently null. I'm sure I'm missing something simple.

Here's both the client and server code:

//client:  <script language="Javascript">  function xmlhttpPost(strURL) {      var xmlHttpReq = false;      var self = this;      // Mozilla/Safari      if (window.XMLHttpRequest) {          self.xmlHttpReq = new XMLHttpRequest();      }      // IE      else if (window.ActiveXObject) {          self.xmlHttpReq = new ActiveXObject("Microsoft.XMLHTTP");      }      self.xmlHttpReq.open('POST', strURL, true);      self.xmlHttpReq.setRequestHeader('Content-Type', 'application/x-www-form-urlencoded');      self.xmlHttpReq.onreadystatechange = function() {          if (self.xmlHttpReq.readyState == 4) {              //updatepage(self.xmlHttpReq.responseText);              alert('test '+self.xmlHttpReq.responseText);          }      }      self.xmlHttpReq.send();  }  </script>      //server (SuiteLet):  function demoList(request, response)   {      response.write('<b>yo baby</b>');  }