How to use async?

[Keavon]

Testing the demo, it works to successfully read my metadata from an MP3 file with the async box unchecked. However, when I check the box, it does not read the metadata and gives the console error
Uncaught SyntaxError: Failed to execute 'importScripts' on 'WorkerGlobalScope': The URL 'taglib.js' is invalid.

Edit: I see I have to specify an exact path to taglib.js in the async call which is http://localhost:8000/taglib.js in the example. New question: Is it possible to use a relative path?