Handling error with typescript problem

[oskar-gmerek]

Hello,

I'm learning so please do not beat me ;)

{newUserMutation.isError && <p>{newUserMutation.error?.message}</p>}

That line of code is working as expected, but when I trying to build a project, then I getting that error:

Type error: Property 'message' does not exist on type 'unknown'.

Is there anyone who will be able help me to sort it out?

Kind Regards,
Oskar

[TkDodo]

in JavaScript, you can throw anything, it doesn't have to be an Error. If you throw 5, error would be a number. In TypeScript, since v4.4, if you use try/catch, the error you get in the catch clause will also be of type unknown. So you need to narrow it first, e.g. with:

{newUserMutation.error instanceOf Error && <p>{newUserMutation.error?.message}</p>}

I am covering this in my blog here: https://tkdodo.eu/blog/react-query-and-type-script#what-about-error

[oskar-gmerek]

Thank you so much. I was looked at your blog before writing that question, but missed that part.

Btw. Great blog!

[dindustack]

Thanks, this solved my issue