TypeScript - Define a subset of type

Question

Say I have a type like so:

interface IAll {
  foo: boolean,
  bar: Function,
  baz: number
}

instead of manually defining all the possible subtypes of IAll, like so:

interface IAll1 {
  foo: boolean,
  bar: Function,
}

interface IAll2 {
  bar: Function,
  baz: number
}

interface IAll3 {
  foo: boolean,
}

interface IAll4 {
  foo: boolean,
}

...etc

and then doing

type IAll = IAll1 | IAll2 | IAll3 ... etc.

Is there a way for TypeScript to statically check whether an object is a subtype or subset of another?

This is useful for some cases where we combine several subtypes or subsets to form a full type.

Answer 1

You can use Partial<T>. This will make all the properties in IAll optional:

type SubsetOfIAll = Partial<IAll>;