What is vending machine?

Obviously, the assignment is to make an analogy from the real world. Although optimized online version of the vending machine would be easier to use. Since in the real world the money insterted by parts:

1. We need to keep the amount of inserted money;
2. We need to give change.

The strangeness of the task

Represent a basic data model that underlays the functionality
Prototype (quickly) a simple UI that allows the user to interact with the machine

i.e. I have to make a class that is not related to UI. It's weird, because in my opinion it should deal with the backend, but it is not required. What's the point in client code if its functionality can not be applied?

What libraries to use?

Nothing. Why:

1. React has a built-in mechanism to work with state.
2. We don't have much related data (components).
3. Solution should be as simple as possible. The easier it is to read the code – the better.
4. We don't need a backend.

Ok, I'm gonna to create first version.

UPD:

I think I've understood. You need to imagine that we are not writing a web page, but a code that will be executed directly on the vending machine. Let's try.