How to set the structure of an object in the interface, with a mandatory key and any number of another type?

Question

JavaScript

There is such a structure for writing commands:

export interface cmd {
    _about: string,
    id: number,
}
export interface category {
    _about: string,//Вот тут проблема
    [cmd: string]: cmd
}
export interface cmdList {
    [category: string]: category
}

const list: cmdList = {
    system: {
        _about: "Системные команды",
        ok: {
            _about: "Успешно принятая команда",
            id: 0
        },
        err: {
            _about: "Ошибка принятие команды",
            id: 1
        }
    }
};

How to correctly set the required field _about of type string in category, and all other fields of type cmd?

Answer 1

https://basarat.gitbooks.io/typescript/docs/types/... section "Excluding certain properties from the index signature"
In your case it will look like this .
It's better to construct this object differently:

{
  system: {
    _about: ...,
    commands: {
      ok: { ... },
      err: { ... }
    }
  }
}