Ajax tutorial

I am reading this tutorial about AJAX
http://www-128.ibm.com/developerworks/java/library/j-ajax1/

Code to send AJAX HTTP Request:

function addToCart(itemCode) {

// Obtain an XMLHttpRequest instance
var req = newXMLHttpRequest();

// Set the handler function to receive callback notifications
// from the request object
var handlerFunction = getReadyStateHandler(req, updateCart);
req.onreadystatechange = handlerFunction;

// Open an HTTP POST connection to the shopping cart servlet.
// Third parameter specifies request is asynchronous.
req.open("POST", "cart.do", true);

// Specify that the body of the request contains form data
req.setRequestHeader("Content-Type",
                     "application/x-www-form-urlencoded");

// Send form encoded data stating that I want to add the
// specified item to the cart.
req.send("action=add&item="+itemCode);
}

The Ajax community is fast moving. JSON is an alternative to the
XML data.
representation