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Contents
import type {Simplify} from './simplify';
// Returns `never` if the key is optional otherwise return the key type.
type RequiredFilter<Type, Key extends keyof Type> = undefined extends Type[Key]
? Type[Key] extends undefined
? Key
: never
: Key;
// Returns `never` if the key is required otherwise return the key type.
type OptionalFilter<Type, Key extends keyof Type> = undefined extends Type[Key]
? Type[Key] extends undefined
? never
: Key
: never;
/**
Enforce optional keys (by adding the `?` operator) for keys that have a union with `undefined`.
@example
```
import type {EnforceOptional} from 'type-fest';
type Foo = {
a: string;
b?: string;
c: undefined;
d: number | undefined;
};
type FooBar = EnforceOptional<Foo>;
// => {
// a: string;
// b?: string;
// c: undefined;
// d?: number;
// }
```
@internal
@category Object
*/
export type EnforceOptional<ObjectType> = Simplify<{
[Key in keyof ObjectType as RequiredFilter<ObjectType, Key>]: ObjectType[Key]
} & {
[Key in keyof ObjectType as OptionalFilter<ObjectType, Key>]?: Exclude<ObjectType[Key], undefined>
}>;
Version data entries
28 entries across 28 versions & 2 rubygems