/*

  * Custom input mask for the address field's international scheme.

  *  

  * @link https://wpforms.com/developers/how-to-add-an-input-mask-to-the-international-postal-code

*/

function wpf_dev_address_field_properties( $properties, $field, $form_data ) {

    if($field[ 'scheme' ] === 'international') {

        $properties[ 'inputs' ][ 'postal' ][ 'class' ][]                  = 'wpforms-masked-input';

        $properties[ 'inputs' ][ 'postal' ][ 'data' ][ 'inputmask-mask' ]   = '999999';

        $properties[ 'inputs' ][ 'postal' ][ 'data' ][ 'inputmask-greedy' ] = 'false';

        $properties[ 'inputs' ][ 'postal' ][ 'data' ][ 'rule-empty-blanks' ] = true;

    }

  return $properties; 

}

 add_action( 'wpforms_field_properties_address', 'wpf_dev_address_field_properties', 10, 3 )