在 Typescript 中如何实现类型标记 Pick 与 Omit

更多描述有以下测试用例

interface User {
  id: number;
  age: number;
  name: string;
}
 
// 相当于: type PickUser = { age: number; name: string; }
type OmitUser = Omit<User, "id">;
 
// 相当于: type PickUser = { id: number; age: number; }
type PickUser = Pick<User, "id" | "age">;

Issue 欢迎在 Gtihub Issue 中回答此问题: Issue 695

Author 回答者: shfshanyue

type Pick<T, K extends keyof T> = {
  [P in K]: T[P];
};
 
type Exclude<T, U> = T extends U ? never : T;
 
type Omit<T, K extends keyof any> = Pick<T, Exclude<keyof T, K>>;

interface User {
  id: number;
  age: number;
  name: string;
}
 
// 相当于: type PickUser = { age: number; name: string; }
type OmitUser = Omit<User, "id">;
 
// 相当于: type PickUser = { id: number; age: number; }
type PickUser = Pick<User, "id" | "age">;

Author 回答者: Asarua

type MyPick<O extends object, K extends keyof O> = {
  [P in K]: O[P];
};
 
type MyOmit<O extends object, K extends keyof O> = MyPick<
  O,
  Exclude<keyof O, K>
>;
 
type MyOmit2<O extends object, K extends keyof O> = {
  [P in Exclude<keyof O, K>]: O[P];
};

汇总【Q692】什么是协变与逆变