UnionToIntersection type

Turns a union into the intersection of its members: A | B gives A & B, to merge the types of a list of mixins or handlers.

import type { UnionToIntersection } from 'utils';

Signature

export type UnionToIntersection<U> = (U extends unknown ? (value: U) => void : never) extends (value: infer I) => void
  ? I
  : never;

Parameters

Name	Description
U	The members to intersect, as a union.

Example

type All = UnionToIntersection<{ a: 1 } | { b: 2 }>; // { a: 1 } & { b: 2 }

Tests

Line coverage: 0 %.

• ✅ intersects the members

Source

src/types/union-to-intersection.ts (on GitHub)

Source code

/**
 * Turns a union into the intersection of its members: `A | B` gives `A & B`, to merge the types of a list
 * of mixins or handlers.
 *
 * @template U - The members to intersect, as a union.
 * @example
 * type All = UnionToIntersection<{ a: 1 } | { b: 2 }>; // { a: 1 } & { b: 2 }
 */
export type UnionToIntersection<U> = (U extends unknown ? (value: U) => void : never) extends (value: infer I) => void
  ? I
  : never;

Test file

import type { UnionToIntersection } from './union-to-intersection';

describe('UnionToIntersection', () => {
  it('intersects the members', () => {
    expectTypeOf<UnionToIntersection<{ a: 1 } | { b: 2 }>>().toEqualTypeOf<{ a: 1 } & { b: 2 }>();
  });
});

Keywords: union, to, intersection, types, type