0. Implementation of setState (explained)

implementation of setState updates the state object directly, which can be more performant than creating a new state object with each update. This is because creating a new state object with each update can be memory-intensive, especially in cases where the state object is large or updates are frequent.

In contrast, updating the existing state object directly can be more efficient, as it avoids creating new objects and can result in less memory usage. This approach can be appropriate for small or infrequently updated state objects, where the benefits of immutable updates may not be as significant.

However, keep in mind that direct updates can also make it harder to reason about state changes, as it can be more difficult to track changes over time. Additionally, direct updates can make it harder to implement features such as undo/redo or time-travel debugging, which rely on maintaining a history of state changes.

Ultimately, the choice between direct updates and immutable updates will depend on the specific use case and the trade-offs between performance and other factors such as maintainability and flexibility.