Check The Password Confirmation With Yup

The Yup library makes it easy to validate individual values in a JavaScript object. A common situation when implementing a Sign Up form is asking the user to input their password twice and then the app can make sure they match.

To do this, we need the validation of our passwordConfirmation value to reach outside of itself to make a comparison with the password value. This can be done with Yup's ref function.

import * as Yup from 'yup';

validationSchema: Yup.object({
  password: Yup.string().required('Password is required'),
  passwordConfirmation: Yup.string()
     .oneOf([Yup.ref('password'), null], 'Passwords must match')
});

We are able to reference the value of password with ref. We use the oneOf function to ensure that passwordConfirmation either matches password or if it is left blank and matches null then it passes the validation for the time being. The second argument to oneOf is a custom validation message when this validation fails.

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