Metadata and extensions.

I want to write metadata to any file. Is that possible?

And what about folders, can I write metadata to a folder?

Could any one help me by modifying this js code snippet to acheive that:

app.synchronousMode = true;
var pathToLib = Folder.startup.fsName + "/AdobeXMPScript.framework";
var xmpLib = new ExternalObject ("lib:" + pathToLib);
var thumb = app.document.selections[0];
var myFile = thumb.spec;
var myXmpFile =  new XMPFile(myFile.fsName, XMPConst.UNKNOWN, XMPConst.OPEN_FOR_UPDATE);
var myXmp = myXmpFile.getXMP();
myXmp.setLocalizedText( XMPConst.NS_DC, "title", null, "x-default", "Some Text");
var updatedPacket = myXmp.serialize(XMPConst.SERIALIZE_OMIT_PACKET_WRAPPER | XMPConst.SERIALIZE_USE_COMPACT_FORMAT);
thumb.metadata = new Metadata(updatedPacket);
myXmpFile = new XMPFile (myFile.fsName, XMPConst.UNKNOWN, XMPConst.OPEN_FOR_READ);
myXmp = myXmpFile.getXMP();
var myTitle = myXmp.getProperty (XMPConst.NS_DC, "title[1]");
$.writeln (myTitle +""); 
app.synchronousMode = false;

Thanks for any one read this, and much thanks for any answer.