# Type.Mapped

Applies a Mapped operation to a type.

> ⚠️ This function is a Script evalutation action.

## Example

Example usage is shown below.

    const T = Type.Object({
      x: Type.Number(),
      y: Type.Number(),
      z: Type.Number()
    })

                                                        // type S = {
                                                        //   [K in keyof T]: T[K] | null
                                                        // }

    const S = Type.Mapped(                              // const S: TObject<{
      Type.Identifier('K'),                             //   x: TUnion<[TNumber, TNull]>,
      Type.KeyOf(T),                                    //   y: TUnion<[TNumber, TNull]>,
      Type.Ref('K'),                                    //   z: TUnion<[TNumber, TNull]>,
      Type.Union([                                      // }>
        Type.Index(T, Type.Ref('K')),
        Type.Null()
      ])
    )