My DMAS Calculator (feedback appreciated)

Hi everyone,

I’m a 46 yr old professional cellist.
18 months ago I couldn’t write a line of code. Since then I’ve devoted a few hours a week to coding (working through the FCC Curriculum), with a view to a career change in the next year or two.

Here’s my attempt at one of the FCC Frontend Libraries projects:

(I removed the test suite but it passes all of the tests and I’ve successfully submitted it).

I have commented my code as best I can, including a README at the top of the JS.
I’d appreciate any feedback you can offer me, good or bad…

Many thanks!