将 object 中的特定类型的值转换为 TypeScript 中的另一种类型

Question

Hi I want to declare a type from another type, eg

// from this type
type Source = {
  id: string
  name: string
  price: Decimal
  createdAt: Date
}

// want to create this type
// Decimal and Date types are converted to string while other fields are kept untouched
type Destination = {
  id: string
  name: string
  price: string
  createdAt: string
}

// It is desired to declare the destination type with some generics:
type Destination = SomeGenerics<Source>;

Is it possible using TypeScript type manipulation ?

Context: After JSON.stringify an object and JSON.parse , the fields with type Decimal or Date are converted into string. I want to create a type for the resulting object in the most effortless way, since there are many source types and declaring all the destination types by hand is hard to maintain.

Answer 1

type JsonConverter<T extends Record<string, unknown>> = {[key in keyof T]: ToStringIfExtends<T[key], Date | Decimal>}

type ToStringIfExtends<K, E> = K extends E ? string : K