Function maskNic

maskNic(input: unknown, visibleDigits?: number): string | null
Masks a valid NIC for display. Returns null for invalid input.
Parameters
- input: unknown
  NIC number.
- visibleDigits: number = 4
  Characters to leave visible at the end. Defaults to 4; invalid values reveal nothing.
Returns string | null
The masked NIC, or null if the NIC is invalid.
Example
```
maskNic('921234567V'); // '******567V'
maskNic('921234567V', 0); // '**********'
```
- Defined in privacy/redaction.ts:46