React 状态存储整数值的默认值

Question

I have a selectedId React state that stores integer values. The state is updated with an id integer, when an item is selected from a list. Once selectedId is set, the user can click a delete button to delete the selected element, after which selectedId should be set back to its initial value again.

What is the recommended default value for selectedId ? Should it set to null ( useState(null) and setSelectedId(null) ), or be undefined ( setSelectedId() )

const [selectedId, setSelectedId] = useState();

const handleSelect = id => {
  setIsAlertOpen(true);
  setSelectedId(id);
};

<Button onClick={() => {
  deleteItem(selectedId)
  setSelectedId();
}/>

Answer 1

Create a constant to store the initial value. And when you delet the selectid restore it yo initial value.

const initialValue = null;
const [selectedId, setSelectedId] = useState(initialValue);

const handleSelect = id => {
  setIsAlertOpen(true);
  setSelectedId(id);
};

<Button onClick={() => {
  deleteItem(selectedId)
  setSelectedId(initialValue);
}/>