Only call Hooks from React functions

Don’t call Hooks from regular JavaScript functions. Instead, you can:

✅ Call Hooks from React function components. ✅ Call Hooks from custom Hooks (we’ll learn about them on the next page).

By following this rule, you ensure that all stateful logic in a component is clearly visible from its source code.

function FriendList() {
  const [onlineStatus, setOnlineStatus] = useOnlineStatus(); // ✅
}

function setOnlineStatus() { // ❌ Not a component or custom hook!
  const [onlineStatus, setOnlineStatus] = useOnlineStatus();
}