Function convertNewToOldNic

convertNewToOldNic(
newNic: unknown,
options?: NicOptions & { isVoter?: boolean },
): string | null
Converts a 12-digit New Sri Lankan NIC into a 10-character Old NIC if the birth year is between 1900 and 1999. Note: If the 4-digit serial does not start with '0', conversion is strictly lossy/incompatible. Format: YY + DDD + SSS + C + (V or X)
Parameters
- newNic: unknown
  New-format 12-digit NIC.
- Optionaloptions: NicOptions & { isVoter?: boolean }
  Optional { referenceDate, isVoter }. isVoter: false produces the X suffix; the default is V.
Returns string | null
The equivalent old-format NIC, or null if the input is invalid or the holder was not born between 1900 and 1999.
Example
```
convertNewToOldNic('199212304567'); // '921234567V'
convertNewToOldNic('199212304567', { isVoter: false }); // '921234567X'
convertNewToOldNic('200012304567'); // null
```
- Defined in nic/converter.ts:42