requiredByKeys
题目
Github: requiredByKeys
实现一个通用的RequiredByKeys<T, K>，它接收两个类型参数T和K。
K指定应设为必选的T的属性集。当没有提供K时，它就和普通的Required<T>一样使所有的属性成为必选的。
interface User {
name?: string
age?: number
address?: string
}
type UserRequiredName = RequiredByKeys<User, 'name'>
// { name: string; age?: number; address?: string }解题思路
略。
答案
type RequiredByKeys<T, K extends keyof T = keyof T> = Omit<{
[P in keyof T as P extends K ? P : never]-?: T[P]
} & {
[P in keyof T as P extends K ? never : P]: T[P]
}, never>验证
interface User {
name?: string
age?: number
address?: string
}
interface UserRequiredName {
name: string
age?: number
address?: string
}
interface UserRequiredNameAndAge {
name: string
age: number
address?: string
}
type cases = [
Expect<Equal<RequiredByKeys<User, 'name'>, UserRequiredName>>,
Expect<Equal<RequiredByKeys<User, 'name' | 'age'>, UserRequiredNameAndAge>>,
Expect<Equal<RequiredByKeys<User>, Required<User>>>,
// @ts-expect-error
Expect<Equal<RequiredByKeys<User, 'name' | 'unknown'>, UserRequiredName>>,
]