Type Alias HasProperty<T, K>

HasProperty: K extends keyof T ? true : false

Test if an object has a specific property.

Type Parameters

T
The object type
K extends PropertyKey
The property key to check

Remarks

Distinguishes between properties that are missing vs. undefined. Useful for generic type checks in mapped or conditional types.

Example

type Obj = { a: string; b?: number };
type Has_a = HasProperty< Obj, 'a' >;  // true
type Has_c = HasProperty< Obj, 'c' >;  // false