Returns a ConstMap containing the values of the current ConstMap that meet a supplied condition

public function filter(
  (function(Tv): bool) $fn,
): ConstMap<Tk, Tv>;

Only values that meet a certain criteria are affected by a call to filter(), while all values are affected by a call to map().

The keys associated with the current ConstMap remain unchanged in the returned ConstMap.



  • (function(Tv): bool) $fn - The callback containing the condition to apply to the current ConstMap values.


  • ConstMap<Tk,Tv> - a Map containing the values after a user-specified condition is applied.