It checked that username match alpha regex or not
If you want to apply conditional validation on 'Contact Number' or 'Age', then you need to add 'userName' input as 'Bharat
{{userFormGroup.controls.userName.errors.pattern.message}}
It checked that zipcode match zipcode regex or not
Shows custom message
{{userFormGroup.controls.zipCode.errors.pattern.message}}
It checked that age match with digit regex or not and it conditionaly applied when userName is Bharat
Conditional Expression with type 'string'
{{userFormGroup.controls.age.errors.pattern.message}}