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Deep Readonly

介绍​

实现通用DeepReadonly<T>,让对象的每个参数-且子对象迭代只读

你可以假设在这个挑战中我们只处理对象. 数组, 函数, 类等等不需要考虑. 然而, 你仍然可以通过处理尽可能多的不同案例来挑战自己.

For example

ts
type X = {
  x: {
    a: 1
    b: 'hi'
  }
  y: 'hey'
}
type Expected = {
  readonly x: {
    readonly a: 1
    readonly b: 'hi'
  }
  readonly y: 'hey'
}
const todo: DeepReadonly<X> // should be same as `Expected`
ts
type X = {
  x: {
    a: 1
    b: 'hi'
  }
  y: 'hey'
}
type Expected = {
  readonly x: {
    readonly a: 1
    readonly b: 'hi'
  }
  readonly y: 'hey'
}
const todo: DeepReadonly<X> // should be same as `Expected`
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起点​

ts
/* _____________ Your Code Here _____________ */
 
type DeepReadonly<T> = any
 
/* _____________ Test Cases _____________ */
type cases = [
  Expect<Equal<DeepReadonly<X>, Expected>>,
Type 'false' does not satisfy the constraint 'true'.2344Type 'false' does not satisfy the constraint 'true'.
]
 
type X = {
  a: () => 22
  b: string
  c: {
    d: boolean
    e: {
      g: {
        h: {
          i: true
          j: 'string'
        }
        k: 'hello'
      }
    }
  }
}
 
type Expected = {
  readonly a: () => 22
  readonly b: string
  readonly c: {
    readonly d: boolean
    readonly e: {
      readonly g: {
        readonly h: {
          readonly i: true
          readonly j: 'string'
        }
        readonly k: 'hello'
      }
    }
  }
}
ts
/* _____________ Your Code Here _____________ */
 
type DeepReadonly<T> = any
 
/* _____________ Test Cases _____________ */
type cases = [
  Expect<Equal<DeepReadonly<X>, Expected>>,
Type 'false' does not satisfy the constraint 'true'.2344Type 'false' does not satisfy the constraint 'true'.
]
 
type X = {
  a: () => 22
  b: string
  c: {
    d: boolean
    e: {
      g: {
        h: {
          i: true
          j: 'string'
        }
        k: 'hello'
      }
    }
  }
}
 
type Expected = {
  readonly a: () => 22
  readonly b: string
  readonly c: {
    readonly d: boolean
    readonly e: {
      readonly g: {
        readonly h: {
          readonly i: true
          readonly j: 'string'
        }
        readonly k: 'hello'
      }
    }
  }
}
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解决方案​

Spoiler warning // Click to reveal answer
ts
type DeepReadonly<T> = {
  readonly [P in keyof T]: keyof T[P] extends never ? T[P] : DeepReadonly<T[P]>
}
ts
type DeepReadonly<T> = {
  readonly [P in keyof T]: keyof T[P] extends never ? T[P] : DeepReadonly<T[P]>
}
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