How to specify type of UseState output in typescript react

Question

I've got a variable whose initial value I want to be null , but I want to be able to set it as a number as well.

const [intervalId, setIntervalId] = useState(null);

When I write setIntervalId(2); in my code later, it complains that argument type number is not assignable to SetActionState<null> .

What's the proper way to define such a variable in React?

Answer 1

很简单：

const [intervalId, setIntervalId] = useState<null | number>(null);