Javascript fetch API doesn’t return

I’m running an HTTP server with python -m http.server that’s serving my ressources.
Here’s my layout :

dist/
   bundle.js
   index.html
   style.css
assets/
   tracks/
       listing.json

I have the following code :

fetch("http://localhost:8000/assets/tracks/listing.json")
    .then(() => console.log("Got it"))

So far so good, it prints ‘Got it’ after a few ms.
But when I do that :

fetch("http://localhost:8000/assets/tracks/listing.json")
    .then(() => console.log("Got it"))

while (true) {}

It just somehow freezes without printing anything, and the page has that little blue circle indicating it’s still loading.

I have a way of not using that while loop, and, so to say, to solve the problem.
But I think this has something to do with how asynchronous processes work in Javascript, and I think it could be good for me to learn a bit more about exactly why it doesn’t work.

Thanks !