Typescript Magic

############################
# USE TYPE AS KEY OF OBJECT#
############################
type DayOfTheWeek = "sunday" | "monday" | "tuesday" | "wednesday" | "thursday" | "friday" | "saturday";

type ChoresMap = { [day in DayOfTheWeek]: string };

const chores: ChoresMap = { // ERROR! Property 'saturday' is missing in type '...'
    "sunday": "do the dishes",
    "monday": "walk the dog",
    "tuesday": "water the plants",
    "wednesday": "take out the trash",
    "thursday": "clean your room",
    "friday": "mow the lawn",
};

##########################################
# USE TYPE AS KEY OF OBJECT with GENERICS#
##########################################
type DayOfTheWeek = "sunday" | "monday" | "tuesday" | "wednesday" | "thursday" | "friday" | "saturday";

type DayOfTheWeekMap<T> = { [day in DayOfTheWeek]: T };

const chores: DayOfTheWeekMap<string> = {
    "sunday": "do the dishes",
    "monday": "walk the dog",
    "tuesday": "water the plants",
    "wednesday": "take out the trash",
    "thursday": "clean your room",
    "friday": "mow the lawn",
    "saturday": "relax",
};

const workDays: DayOfTheWeekMap<boolean> = {
    "sunday": false,
    "monday": true,
    "tuesday": true,
    "wednesday": true,
    "thursday": true,
    "friday": true,
    "saturday": false,
}

#########################
#EXCLUDE ITEMS FROM TYPE#
#########################

interface CreditCardOwnerInformationUIDTO {
  floor: string;
  department: string;
  postalCode: string;
}

type TGetValues = Pick<
  CreditCardOwnerInformationUIDTO,
  Exclude<keyof CreditCardOwnerInformationUIDTO, 'floor' | 'department'>
>;

// TGetValues should be = postalCode: string;


##################################
# UNION TYPE BASED ON OBJECT KEYS#
##################################

const paymentTypes = {
  prepaid: 'foo',
  at_destination: 'bar',
  advance_payment: 'foo bar',
};

type p = keyof typeof paymentTypes;

// P must be = "prepaid" | "at_destination" | "advance_payment";

##################################
# MAKE ALL PROPERTIES OPTIONAL   #
##################################
type Optionals<T> = {
  [P in keyof T]?: T[P];
};


##################################
##### MORE MAGIC #################
##################################
https://stackoverflow.com/questions/13315131/enforcing-the-type-of-the-indexed-members-of-a-typescript-object

export interface StringTMap<T> { [key: string]: T; };
export interface NumberTMap<T> { [key: number]: T; };

export interface StringAnyMap extends StringTMap<any> {};
export interface NumberAnyMap extends NumberTMap<any> {};

export interface StringStringMap extends StringTMap<string> {};
export interface NumberStringMap extends NumberTMap<string> {};

export interface StringNumberMap extends StringTMap<number> {};
export interface NumberNumberMap extends NumberTMap<number> {};

export interface StringBooleanMap extends StringTMap<boolean> {};
export interface NumberBooleanMap extends NumberTMap<boolean> {};