How to test for uniqueness of value in Yup.array?

Question

I have form with dynamic amount of inputs (admin email) however checking for uniqueness fails:

      validationSchema={Yup.object().shape({
        adminEmails: Yup.array()
          .of(
            Yup.string()
              .notOneOf(Yup.ref('adminEmails'), 'E-mail is already used')

What is best approach here? FYI, as a form helper I use Formik.

Answer 1

Try this:

Yup.addMethod(Yup.array, 'unique', function(message, mapper = a => a) {
    return this.test('unique', message, function(list) {
        return list.length  === new Set(list.map(mapper)).size;
    });
});

Then use it like this:

const headersSchema = Yup.object().shape({
    adminEmails: Yup.array().of(
        Yup.string()
    )
    .unique('email must be unique')
})