Typescript Type Flatten Child nested objects

Question

i have been following this example and here to flatten a type invain. Most of this flatten the object completely into removing the nests. I would like to to maintain my structure, just removing some wrappers (in this case body) in the nested objected which can be anything and n deep.

I would like to transform my type from

type TestInterface {
  id: string
  body: {
    title: string 
    something: string 
    user: {
      id: string
      body: {
        firstname: string
        lastname: string
        age: number
      }
    }
    country: {
      id: string
      body: {
        code: string
        name: string
        region: {
          id: string
          body: {
            code: string
            name: string
            continent: {
              id: string
              body: {
               code: string
               name: string
              }
            }
          }
        }
      }
    }
  }
}

the required output is the same type structure above but with the body wrapper dropped.

type TestInterface {
  id: string
  title: string 
  something: string 
  user: {
    id: string
    firstname: string
    lastname: string
    age: number
  }
  country: {
    id: string
    code: string
    name: string
    region: {
      id: string
      code: string
      name: string
      continent: {
        id: string
        code: string
        name: string
      }
    }
  }
}

Dimava · Accepted Answer · 2022-11-17 07:16:39Z

0

type Pure<T> = T extends object ? {[K in keyof T]: T[K]} : T
type Flatten<T> = Pure<
| T extends {body: any} ? Flatten2<Omit<T, 'body'> & T['body']> : Flatten2<T>
>
type Flatten2<T> = T extends object ? {[K in keyof T]: Flatten<T[K]>} : T

type X = Flatten<TestInterface>

Playground

answered Nov 17, 2022 at 7:16

Dimava

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2 Comments

muturiken Over a year ago

thanks @Dimava. this works appreciated

muturiken Over a year ago

i am extending this to a generic it kind looses the types. see line 68 - 74 that organization can not be reached. playground

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