8 - 对象部分属性只读

fxss原创2025/4/29大约 1 分钟

8 - 对象部分属性只读

by Anthony Fu (@antfu) #中等 #readonly #object-keys

题目

实现一个泛型MyReadonly2<T, K>，它带有两种类型的参数T和K。

类型 K 指定 T 中要被设置为只读 (readonly) 的属性。如果未提供K，则应使所有属性都变为只读，就像普通的Readonly<T>一样。

例如

interface Todo {
  title: string
  description: string
  completed: boolean
}

const todo: MyReadonly2<Todo, 'title' | 'description'> = {
  title: "Hey",
  description: "foobar",
  completed: false,
}

todo.title = "Hello" // Error: cannot reassign a readonly property
todo.description = "barFoo" // Error: cannot reassign a readonly property
todo.completed = true // OK

在 Github 上查看：https://tsch.js.org/8/zh-CN

代码

/* _____________ 你的代码 _____________ */

type MyReadonly2<T, K extends keyof T = keyof T> = {
  readonly [P in K]: T[P]
} & Omit<T, K>

测试用例

/* _____________ 测试用例 _____________ */
import type { Alike, Expect } from '@type-challenges/utils'

type cases = [
  Expect<Alike<MyReadonly2<Todo1>, Readonly<Todo1>>>,
  Expect<Alike<MyReadonly2<Todo1, 'title' | 'description'>, Expected>>,
  Expect<Alike<MyReadonly2<Todo2, 'title' | 'description'>, Expected>>,
  Expect<Alike<MyReadonly2<Todo2, 'description' >, Expected>>,
]

// @ts-expect-error
type error = MyReadonly2<Todo1, 'title' | 'invalid'>

interface Todo1 {
  title: string
  description?: string
  completed: boolean
}

interface Todo2 {
  readonly title: string
  description?: string
  completed: boolean
}

interface Expected {
  readonly title: string
  readonly description?: string
  completed: boolean
}

8 - 对象部分属性只读

8 - 对象部分属性只读

题目

代码

测试用例

相关链接