Does Typescript support “subset types”?

Question

Let\'s say I have an interface:

interface IUser {
  email: string;
  id: number;
  phone: string;
};

Then I have a function that expects a

Answer 1

What you want is this

type Subset<T extends U, U> = U;

this makes sure, that U is a subset of T and returns U as a new type. for example:

interface Foo {
 name: string;
 age: number;
}

type Bar = Subset<Foo, {
 name: string;
}>;

you can not add new properties to Bar which are not part of Foo - and you can not alter types in a non-compatible way. this also works recursively on nested objects.