index signature in TypeScript is an optional feature

Is it possible to create a type with optional namespaces in TypeScript?

export interface NodesState {
  attr1: number;
  attr2: number;
  attr3: number;
}

The goal is to allow users to namespace the type like this:

{
  namespace1: {
    attr1: 100,
    attr2: 150,
    attr3: 200
  },
  namespace2: {
    attr1: 300,
    attr2: 400
  }
}

But also make it legal to have no namespaces, such as:

{
  attr1: 200,
  attr2: 100,
  attr3: 200
}

I've attempted using this code:

export type MakeState<T> = T & {
  [key: string]?: Partial<T>
}

However, TypeScript does not recognize this syntax. Is there a way to achieve what I'm trying to do?

Answer №1

It appears that the solution you are seeking is as follows:

type CreateCustomState<T> = T & { [index: string]: T }

How to use it:

declare const customState: MakeState<NodesState>;

customState.attr1;       // `number`
customState["foo"]       // `NodesState`

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