Function option

option<TToken, TOptions, TValue>(p: Parser<TToken, TOptions, TValue>, def: TValue): Matcher<TToken, TOptions, TValue>
Make a Matcher that returns either a match from a given parser or a match with the default value (without consuming input in that case).

Use otherwise if you want to provide a Matcher instead of a constant default value.
Type Parameters
- TToken
- TOptions
- TValue
Parameters
- p: Parser<TToken, TOptions, TValue>
  
  A parser.
- def: TValue
  
  Default value to be returned in case parser didn't match.
Returns Matcher<TToken, TOptions, TValue>