Fetch API

[Micrufun]

Replace XMLHttpRequest with Fetch API. According to this:

The Fetch API ... will seem familiar to anyone who has used XMLHttpRequest, but the new API provides a more powerful and flexible feature set.

Why?

Fetch API might be helpful when implementing the audio streaming in the future. According to that:

By using the fetch() API, we can stream the data rather than waiting for the whole file to load.

[Micrufun]

Test

Testing the code with npm run dev indicates that it works fine: