Is it possible to restrict typescript object to contain only properties defined by its class?

Question

Here is my code

async getAll(): Promise {
    return await dbQuery(); // dbQuery returns User[]
}

class User {
    id: number;
    na         


        

Answer 1

Following up on GregL's answer, I'd like to add support for arrays and make sure that if you've got one, all the objects in the array have no extra props:

type Impossible = {
  [P in K]: never;
};

export type NoExtraProperties = U extends Array
  ? NoExtraProperties[]
  : U & Impossible>;

Note: The type recursion is only possible if you've got TS 3.7 (included) or above.