Subset Type

Subset is NOT an official feature of Typescript, but is an encouraged pattern.

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

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

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

This makes sure that U is a subset of T and returns U as a new type.

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