How to call a custom hook in a hook?

Question

React

Good evening!
Why can't I call a custom hook in the useEffect hook ?
https://codesandbox.io/s/frosty-pine-yjv6y

Answer 1

Isn't the error text enough for you?))
Invalid hook call. Hooks can only be called inside of the body of a function component.
Invalid hook call. Hooks can only be called inside the body of a functional component.
Well, the codepen itself swears, stating it quite clearly.
React Hook "useCustom" cannot be called inside a callback. React Hooks must be called in a React function component or a custom React Hook function.
I didn’t quite understand the purpose of this action, but here is a clear example of using a custom hook.