The property “XXX” does not exist on type “Readonly<{}>”.

Problems encountered during development are as follows:

JSX is not an error, so I want to type the properties in state, so I found the following method on the Internet:

But an error will be reported:

Merge declaration “test1” cannot contain default export declarations. Consider adding a separate “export default test1” declaration instead.

Delete export default in front of the class component and export it separately.