rest countries api, dark mode, random page, localstorage, nextjs

I've built some custom hooks with the help of the internet, and I think I am getting the hang of it. Does anyone have any tips on creating robust custom hooks?

Also, I was in the process of creating a higher order debounce hook that takes a callback function, but I figured I did not actually need it for this project. However, I am still fascinated with the idea of passing a callback function into a function, and having it return a callback function. Does anyone have any good resources/tips for creating higher order functions in react/next?

Finally, I would like some advice or tips on refactoring code. Do you have any good resources/references on how to best refactor react code? I am slowly making my code a bit nicer to look at, but I still do not know the proper amount of abstraction.