[ts] utility type

1. keyof

interface User {
    id: number;
    name: string;
    age: number;
    gender: "m" | "f";
}

type UserKey = keyof User;

const uk:UserKey = "age"

=> js Object.keys와 비슷한듯

2. Partial< T>

interface User {
    id: number;
    name: string;
    age: number;
    gender: "m" | "f";
}
// interface User {
//     id?: number;
//     name?: string;
//     age?: number;
//     gender?: "m" | "f";
// }

let admin: Partial<User> = {
    id: 1,
    name: "Bob",
}

=> 모든걸 optinal로 바꿔줌

2. Required< T>

interface User {
    id: number;
    name: string;
    age?: number;
    gender: "m" | "f";
}

// interface User {
//     id: number;
//     name: string;
//     age: number;
//     gender: "m" | "f";
// }

let admin: Required<User> = {
    id: 1,
    name: "Bob",
    age: 1,
    gender: "m",
}

3. Record<K, T>

type Grade = "1" | "2" | "3" | "4";
type Score = "A" | "B" | "C" | "D";

const score: Record<Grade, Score> = {
    1: "A",
    2: "C",
    3: "B",
    4: "D",
};

=> Type을 변수로 저장해서 쉽게 관리하면서 쓸 수 있음

interface User {
    id: number;
    name: string;
    age: number;
}

function isValid(user: User) {
    const result: Record<keyof User, boolean> = {
        id: user.id>0,
        name: user.name !== "",
        age: user.age > 0,
    };
    return result;
}

let user: User = {
    id: 1,
    name: 'ts',
    age: 1,
}
console.log(isValid(user));

=> valid에도 이렇게 활용 가능
=> 오. 좋네 생육기록 만들 때, 활용하면 좋을듯
=> 실제로 react form이 이런 형식이였던 것 같은

4. Pick<T, K>

interface User {
    id: number;
    name: string;
    age: number;
    gender: 'M' | 'W';
}

const admin: Pick<User, "id" | "name"> = {
    id: 0,
    name: "Bob",
}

5. Omit<T, K>

interface User {
    id: number;
    name: string;
    age: number;
    gender: 'M' | 'W';
}

const admin: Omit<User, "age" | "gender"> = {
    id: 0,
    name: "Bob",
}

=> Pick과 반대로 얘네들 빼고

6. Exclude<T1, T2>

type T1 = string | number | boolean;
type T2 = Exclude<T1, number | string>;

7. NonNullable< Type>

type T1 = string | null | undefined | void;
type T2 = NonNullable<T1>;