What should I be using intense type checking for?

[latent mica]

Sure I could implement it for everything, but if I am fetching data from an internal/on-prem server and I know the data coming back, should I be type checking the data that is fetched? Are there general rules for making types and when to use types/nested types?

Lets say I have a UI that searches for info based on a phone number or mac address, I would type check the UI input as sort of a sanitization process right? But the data that input fetches does not need to be type checked?

I guess I'm wondering when I should be trying to make intense type checking like so:

type TPhoneNumber = validatePhoneNumber(); // returns string that fits regex for a phone number or something...
type TMacAddress = validateMacAddress(); // similar to above but with regex for mac address...

type TKeyInfo = {
  phoneNumber?: TPhoneNumber;
  macAddress?: TMacAddress;
}

type TKey = 
  | (TKeyInfo & { phoneNumber: TPhoneNumber})
  | (TKeyInfo & { macAddress: TMacAddress});

type TFormData = {
  searchKey: TKey;
  ...OtherFormInputs...
}

Does this seem like good practice, or is it too verbose and pointless?

I want to have a form input that takes either a phone number string or a mac address string, has at least one but can have multiple (running sql searches based on these 'keys').

[tribal tangle]

@latent mica Mostly, I'd suggest keeping the types simple until there's a specific reason to make them more complicated.

If you're finding it hard to keep track of what part of the code is responsible for validating the phone number of the mac address; it can make sense to try to express that validation as part of the type-system (though it's a bit tricky) - but if the validation is just done once when it comes from the API, expressing that nuance in the type system may be unnecessary.

[latent mica]

The backend does not validate the input, and I don't think it will be changed to do so.

I should clarify that the data fetching should probably be a whole different question. I am just wondering about how I should type things for a react form that searches via different types of keys (phone number or Mac address)

[tribal tangle]

I'd probably keep it simple:

type SearchData = {
   kind: "phoneNumber" | "macAddress";
   value: string
}

[latent mica]

I was hoping to find a different way than just having an input field for each and only use one input field