Returns a ConstMap after an operation has been applied to each value in the current ConstMap

public function map<Tu>(
  (function(Tv): Tu) $fn,
): ConstMap<Tk, Tu>;

Every value in the current Map is affected by a call to map(), unlike filter() where only values that meet a certain criteria are affected.

The keys will remain unchanged from the current ConstMap to the returned ConstMap.



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


  • ConstMap<Tk,Tu> - a ConstMap containing key/value pairs after a user-specified operation is applied.