Typescript: SameType

myTypeUtility.txt

/**
 * 由其他generic type組成的會優先保持generic的描述，這樣無法“直接”看到單一property的值。
 * 用這個解構就可以看到property/value的值，debug或查詢蠻方便的。
 */
type FlatPrettified<T extends any> = {
  [P in keyof T]:T[P]
}

/**
 * 改變型別的Optional設定，在資料流的旅程中，有部分的路線是Optional的但又不想放寬整個型別設定。
 */
type MakeSomeFieldsOptional<T, Fields extends keyof T> = Omit<T, Fields> &
  Partial<Pick<T, Fields>>;

/**
 * 改變型別特定property的型別
 */
type ChangeFieldTypes<T, Fields, NewType> = {
  [P in keyof T]: P extends Fields ? NewType : T[P];
};

/**
 * type representation of an array without using an array(but they are fundamentally differerent. Array come with things like length property and method)
 **/
let aa: Record<number, string> = ['1','2','3']
let bb:{ [P in number]: string } = ['1','2','3']
type myArray<T=any> = { [P in number]: T }
let cc:myArray = ['1','2','3'] as unknown as []