IsExtends.md

typelab / assertions / IsExtends

type IsExtends<T1, T2> = _IsTrue<IfExtends<T1, T2, true, false>>;

Type that checks if type T1 extends type T2.

Type Parameters

Type Parameter	Description
T1	The first type to compare.
T2	The second type to compare.

Returns

true if T1 is assignable to T2 (i.e., T1 extends T2), false otherwise.

Example

type Extends = IsExtends<'', string>; // true
type NotExtends = IsExtends<string, ''>; // false