If you're looking for good code, you missed the point of my comment 😄

If I was looking for an enumeration of valid inputs, I'd make it a selection box rather than a text field that's supposed to contain a number and give the selections reasonable names. If I want an integral quantity, I'd use a number input field.

If I have no control over the frontend, that means I'm writing a backend in JS for a bullshit frontend, and no amount of good coding practice is going to salvage this mess.

I'm also blessedly far away from WebDev now. I work in Data Analytics and if I ever have to do any of this for a living, something has gone very wrong.

Converting texts into numbers or dates still haunts me though - fuck text inputs for numbers and dates.