Based on selection of card type conditional validation is applied
{{userForm.controls?.cardType?.errors?.creditCard.message}}
If you want to apply conditional validation on 'Visa Card' then you need to add 'card type' input as 'Visa'.
It shows custom message
Conditional Expression with type 'string'
{{userForm.controls?.otherVisaCard?.errors?.creditCard.message}}
If you want to apply conditional validation on 'American Express' then you need to add 'card type' input as 'AmericanExpress'.
Message comes from Reactive Form Config
{{userForm.controls?.americanExpressCard?.errors?.creditCard.message}}
If you want to apply conditional validation on 'MaestroCard Card' then you need to add 'card type' input as 'Maestro'.
{{userForm.controls?.maestroCard?.errors?.creditCard.message}}
If you want to apply conditional validation on 'JCB Card' then you need to add 'card type' input as 'JCB'.
{{userForm.controls?.jcbCard?.errors?.creditCard.message}}
If you want to apply conditional validation on 'Discover Card' then you need to add 'card type' input as 'Discover'.
{{userForm.controls?.discoverCard?.errors?.creditCard.message}}
If you want to apply conditional validation on 'Master Card' then you need to add 'card type' input as 'MasterCard'.
{{userForm.controls?.masterCard?.errors?.creditCard.message}}
If you want to apply conditional validation on 'Diners Club Card' then you need to add 'card type' input as 'DinersClub'.
{{userForm.controls?.dinersClubCard?.errors?.creditCard.message}}