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@sindresorhus @kainiedziela
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import {Except} from './except';
Create a type that requires at least one of the given properties. The remaining properties are kept as is.
import {RequireAtLeastOne} from 'type-fest';
type Responder = {
text?: () => string;
json?: () => string;
secure?: boolean;
const responder: RequireAtLeastOne<Responder, 'text' | 'json'> = {
json: () => '{"message": "ok"}',
secure: true
export type RequireAtLeastOne<ObjectType, KeysType extends keyof ObjectType = keyof ObjectType> =
// For each Key in KeysType make a mapped type
[Key in KeysType]: (
// …by picking that Key's type and making it required
Required<Pick<ObjectType, Key>>
// …then, make intersection types by adding the remaining properties to each mapped type.
& Except<ObjectType, KeysType>;
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