Type Alias OptionalKeys<T>

OptionalKeys: { [K in keyof T]-?: {} extends Pick<T, K> ? K : never }[keyof T]

Extract the keys of optional properties.

Type Parameters

T
Object type to analyze

Remarks

Identifies properties that are optional in the object type, including properties whose value type explicitly allows undefined.

Example

type Obj = { a: number; b?: string; c: number | undefined; d: boolean };
type OptKeys = OptionalKeys< Obj >;
// "b" | "c"