dataObjects - how does "name" get updated?

Hello
I am trying to use the dataObjects 'function' to return the names of files in a package.

The 'function' works as per the JS API Reference, page 236 for a package comprising several pdf files. However, if I drag and drop new files into the package, the 'function' returns the correct names of the existing files, but returns "Untitled Object" for the newly added file.

The newly added file does have a file name and this appears correctly in the 'package contents' window, it also appears correct if I look to 'edit value' Name after right clicking on the newly added file.

Can any one tell me how to get the file name returned by this function for newly added files?

This is the code I'm using in the console:
var f = this.getField ("ContentsList")
var contents = ""
var d = this.dataObjects;
for (var i = 0; i < d.length; i++)
var contents = contents + d[i].name + "\n";
f.value = contents