feat: allow customizing passing grade

[huyenltnguyen]

Checklist:

• I have read freeCodeCamp's contribution guidelines.
• My pull request has a descriptive title (not a vague title like Update index.md)

Updates useQuiz to allow customizing the passing grade.

Ref: https://github.com/freeCodeCamp/fCC10/issues/2#issuecomment-2391462203.

[huyenltnguyen]

I'm on the fence. I'm not sure if we should have a default value here, or just have it a required prop and ask clients to provide the value.

(#356 already contains a breaking change, so it's not a big deal if we have another here.)

[ojeytonwilliams]

I slightly prefer not defaulting, but either is fine. The main argument for not defaulting is that I don't think that's set in stone, so we may end up having to change it.

[huyenltnguyen]

@ojeytonwilliams I'd like to pick your brain about this 😄

Do you think the initial value of grade and correctAnswerCount should be null instead of 0? Being null would mean that the quiz hasn't been validated, and 0 would mean the quiz has been validated and the value is 0.

That's a little more work for us to handle typing, but client would then be able to conditionally render the grade and correctAnswerCount values using null check, rather than having to pair them with a hasSubmitted boolean.

[ojeytonwilliams]

Good question! I think null (or perhaps undefined) makes sense, mostly because it doesn't seem right to say that someone has a grade or number of correct answers until they have been graded.

One thing to consider is a return type like this:

{ validated: true, grade: number, correctAnswerCount: number, ... } | { validated: false, grade: never, correctAnswerCount: never,  ... }

That way the client can, in principle, just check the value of validated, rather than having to account for both grade and correctAnswerCount being nullable. I say "in principle", because I'm not 100% sure how the code would look in practice, but I think it should work.

[huyenltnguyen]

I went with this because:

• I don't think I can return type never.

  

• And leaving grade and correctAnswerCount out of the return type:

  type ValidationData =
    | { validated: true; grade: number; correctAnswerCount: number }
    | { validated: false };

  Would cause an error in the consumption (in the useQuiz storybook file):

  

[ojeytonwilliams]

I got the type right this time 😰

[ojeytonwilliams]

LGTM 👍