//  stores a reference to an XMLHttpRequest instance
var xmlHttp = createXmlHttpRequestObject();

// retrieves the XMLHttpRequest object
function createXmlHttpRequestObject() 
{
  // will store the reference to the XMLHttpRequest object
  var xmlHttp;
  // this should work for all browsers except IE6 and older
  try
  {
    // try to create XMLHttpRequest object
    xmlHttp = new XMLHttpRequest();
  }
  catch(e)
  {
    // assume IE6 or older
    xmlHttp = new ActiveXObject("Microsoft.XMLHTTP");
  }
  // return the created object or display an error message
  if (!xmlHttp)
    alert("Error creating the XMLHttpRequest object.");
  else 
    return xmlHttp;
}

// make asynchronous HTTP request using the XMLHttpRequest object 
function process()
{
  // proceed only if the xmlHttp object isn't busy
  if (xmlHttp.readyState == 4 || xmlHttp.readyState == 0)
  {
    // retrieve the name typed by the user on the form
    name = encodeURIComponent(document.getElementById("myName").value);
    // execute the Quickstart.aspx page from the server
    xmlHttp.open("GET", "Quickstart.aspx?name=" + name, true);
    // define the method to handle server responses
    xmlHttp.onreadystatechange = handleServerResponse;
    // make the server request
    xmlHttp.send(null);
  }
  else
    // if the connection is busy, try again after one second
    setTimeout("process()", 1000);
}

// executed automatically when a message is received from server
function handleServerResponse()
{
  // move forward only if the transaction has completed
  if (xmlHttp.readyState == 4)
  {
    // status of 200 indicates success
    if (xmlHttp.status == 200)
    {
      // extract the XML retrieved from the server
      xmlResponse = xmlHttp.responseXML;
      // obtain the root element of the XML structure
      xmlDocumentElement = xmlResponse.documentElement;
      // get the text message from the first child of the document 
      helloMessage = xmlDocumentElement.firstChild.data;
      // display the data received from the server
      document.getElementById("divMessage").innerHTML = 
        "<i>" + helloMessage + "</i>";
      // restart sequence
      setTimeout("process()", 1000);
    } 
    // a HTTP status different than 200 signals an error
    else
    {
      alert("There was a problem accessing the server: " + xmlHttp.statusText);
    }
  }
}