Type Alias IsUnion<T, U>

IsUnion: IsNever<T> extends true
? false
: T extends any ? [U] extends [T] ? false : true : false

Type guard: detect whether a type is a union.

Type Parameters

T
Type to test
U = T

Remarks

Resolves to true if T is a union type, otherwise false.

Example

type A = IsUnion< string | number >;  // true
type B = IsUnion< string >;           // false