Type Alias OptionalKeys<T>

OptionalKeys: { [K in keyof T]-?: undefined extends T[K] ? K : never }[keyof T]

Extracts the keys of T that are optional

提取 T 中可选的键

Type Parameters

T extends object

Example

interface Person {
  name: string
  age?: number
  address: string
}
type Keys = OptionalKeys<Person>
// 'age'