Why are you publishing as separate HTML and JS files? There's practically never any reason not to publish with them merged into a single HTML file.
Well anyway, once everything's loaded there's no concept of separate files since everything occupies the same browser namespace. So just replace your hard-coded strings with something like exportRoot.myLabel (exportRoot is a global reference to the root timeline) and make sure it's initialized to a default value somewhere. Then you can change it at will in any other code.