Optional fields

const schema = z.object({
    name: z.string().min(2, 'Name must be at least 2 characters long'),
    email: z.string().email('Invalid email address').optional(),
    age: z.coerce.number().min(18, 'You must be at least 18 years old')
})

const TanstackFormExample = () => {
    const form = useForm({
        defaultValues: {
            name: '',
            email: '',
            age: 12
        },
        validators: {
            onChange: schema
        },
        onSubmit: ({ value }) => {
            console.log(value)
        }
    })

        defaultValues: {
            name: '',
            email: undefined,
            age: 12
        } as z.input<typeof schema>,