AJAX - The Complete Reference

130 Part I: Core Ideas

xhr.setRequestHeader("Content-Type", "text/xml");

xhr.onreadystatechange = function(){handleResponse(xhr);};

xhr.send(payload);

}

}

You can see the transmission of posted XML data in the network trace here, or you can

play with it yourself and run the example at http://ajaxref.com/ch4/xmlrequest.html.

NNOT EOTE You will likely always be using the POST method in the case of passing data beyond the

standard x-www-form-urlencoded format unless you want to take the payload and then

further encode it in that format to be put into the query string.

You might rightfully wonder why we did not use DOM methods to create the XML

packet. We certainly could have, but as you’ll see, it is even more work. First, to address the

various cross-browser issues when working with the XML DOM, it is necessary to abstract

away the creation of the XML document to send. To do so, the wrapper function

createXMLDocument is created.

var xmlDoc = createXMLDocument();

Now in this function, the XML document is created either through Internet Explorer’s

ActiveX approach or the W3C syntax for XML document creation supported in other

browsers.

function createXMLDocument()

{

var xmlDoc = null;

if (window.ActiveXObject)

{

var versions = ["Msxml2.DOMDocument.6.0", "Msxml2.DOMDocument.3.0",

"MSXML2.DOMDocument", "MSXML.DOMDocument", "Microsoft.XMLDOM"];