How get IPTC title for active document in Photoshop CS?

I need to get the document title for the active document (a photo) in Photoshop CS. I have pieced together the following code which runs but does not give me what I want. How do I reference the active Photoshop document and get its title. Thanks.

#target photoshop

// load the library

if (ExternalObject.AdobeXMPScript == undefined) {

    ExternalObject.AdobeXMPScript = new ExternalObject('lib:AdobeXMPScript');

}

xmpRef = new XMPMeta();var xmpMetaRef = new XMPMeta();

var docTitle = xmpRef.getProperty(XMPConst.NS_IPTC_CORE, "Title");

alert(docTitle);