Sometimes when creating a type, we want to make sure that all properties are specified, or none of them are. The AllOrNone type below is useful for defining more precise types.
type AllOrNone<T extends object> = | { [K in keyof T]: T[K]; } | { [K in keyof T]?: never; };type Size = { height: number; width: number;};type Props = AllOrNone<Size>;const all: Props = { height: 200, width: 200 };const none: Props = {};// Property 'width' is missing in type '{ height: number; }' but required in type '{ height: number; width: number; }'.const either1: Props = { height: 200 };// Property 'height' is missing in type '{ width: number; }' but required in type '{ height: number; width: number; }'.const either2: Props = { width: 200 };
