So here is the solution then.
Simply add a GET variable to the declaration.
If you never want the file to be cached, attach a randomly generated GET variable to the .js declaration for each page load. If you want to control when it gets refreshed, add a GET variable that you change only when you make actual changes to the .js file itself.
Essentially what happens is that IE recognises the URL as a single string, meaning that if the GET variable has changed, the string’s identity has changed, meaning a brand new URL and thus something it will need to go and collect from the internet.
So how does one’s .js file include look now?
Simple, but very effective and well worth jotting down.