I have a JS module in the main thread, which can only import regular JS files using dynamic import(). This means that imported functions can never be global.
I also have a web worker (which isn't a module because Mozilla) which can only import other JS files using importScripts(). This means that imported functions can only ever be global.
Effectively I can't use the same code on the main thread and in a worker if it relies on objects defined in other files, because references to these will never be the same.