Typescript類型體操 - RequiredByKeys

題目

中文

實現一個通用的RequiredByKeys<T, K>，它接收兩個類型參數T和K。

K指定應設爲必選的T的屬性集。當沒有提供K時，它就和普通的Required<T>一樣使所有的屬性成爲必選的。

例如:

interface User {
    name?: string;
    age?: number;
    address?: string;
}
type UserRequiredName = RequiredByKeys<User, 'name'>; // { name: string; age?: number; address?: string }

English

Implement a generic RequiredByKeys<T, K> which takes two type argument T and K.

K specify the set of properties of T that should set to be required. When K is not provided, it should make all properties required just like the normal Required<T>.

For example

interface User {
    name?: string;
    age?: number;
    address?: string;
}
type UserRequiredName = RequiredByKeys<User, 'name'>; // { name: string; age?: number; address?: string }

答案

type RequiredByKeys<
    T extends object,
    K extends keyof T | string = keyof T,
    H = {
        [P in K extends keyof T ? K : never]: Exclude<T[P], null | undefined>;
    } & { [P in Exclude<keyof T, K>]?: T[P] }
> = { [P in keyof H]: H[P] };

在線演示