Renaming EPS files

Hi people!

I was trying to rename a few EPS files using this code but it didn't work.

var myEPS = Folder.desktop + '/AF Files/oldName.eps';
myEPS.rename( Folder.desktop + '/AF Files/newName.eps');

I got this code to make it work and I didn't work too! :/

What am I doing wrong?

var myfile = File.openDialog( 'select your AI file…' );
myfile.rename( 'NEW.ai' );

Show this ERROR: myEPS.rename is not a function.

Is possible to rename a file with Illustrator? How could I do it?

Many thanks for your time guys!