object with some specific properties typescript

Question

I have a function that accepts some data and function add some properties and return that parameter object.

this is how I am declaring it

async setContext(@Body() data: { [key: string]: any }): Promise<{
        additionalData: { id: string, [key: string]: any },
        context: Context,
        [key: string]: any
    }> {
        data.additionalData.id = this._getId(data.additionalData);
        data.context = this._getContext();
        return data;
}

but this is showing

Type '{ [key: string]: any; }' is missing the following properties from type '{ [key: string]: any; additionalData: { [key: string]: any; id: string; }; context: Context; }': additionalData, contextts(2739)

so I tried

async setContext(@Body() data: { additionalData?: any, context?: Context, [key: string]: any }): Promise<{
        additionalData: { id: string, [key: string]: any },
        context: Context,
        [key: string]: any
    }> {
        if (!data.additionalData) {
            data.additionalData = {};
        }
        data.additionalData.id = this._getConversationId(data.additionalData);
        data.context = this._getContext();
        return data;
}

but now this is showing

Type '{ [key: string]: any; additionalData?: any; context?: Context; }' is not assignable to type '{ [key: string]: any; additionalData: { [key: string]: any; id: string; }; context: Context; }'.
  Property 'additionalData' is optional in type '{ [key: string]: any; additionalData?: any; context?: Context; }' but required in type '{ [key: string]: any; additionalData: { [key: string]: any; id: string; }; context: Context; }'.ts(2322)

should not this work as I am declaring data as

data: { [key: string]: any }

to have any unknown properties?

question from:https://stackoverflow.com/questions/65914835/object-with-some-specific-properties-typescript

Answer 1

I would define the returned type of the function depending on the type of parameters of the function.

---

Playground

---

To use it in your case, just replace 'foo' and 'bar' by your functions.

---

type Context = string;

type DataIn = { 
  additionalData?: unknown;
  context?: Context;
  [key: string]: unknown;
};

type DataOut = Omit<Required<DataIn>, 'additionalData'> & {
  additionalData: { 
    id: string;
    [key: string]: unknown;
  };
};

async function setContext(data: DataIn): Promise<DataOut> {
  return {
    ...data,

    additionalData: {
      ...(data.additionalData as object),

      id: 'foo',
    },

    context: 'bar',
  };
}

(async() => {
  const myData = await setContext({
    animal: 'dog',
  });

  console.log(myData);
})();