Short summary
Given:
Type: Any type
Provide:
A type that only includes properties from Type that don't have a value of type never.
Potential definition
type NonNeverKeys<Type> = {
[Key in keyof Type]: IsNever<Type[Key]> extends true ? never : Key;
}[keyof Type];
type PickNonNever<Type> = Pick<Type, NonNeverKeys<Type>>;Example usage
type Example = {
[Key in keyof string]: Key extends `${string}At` ? Key : never;
};
type StringSearchable = PickNonNever<Example>;Use case
Removing a set of members from an object via multiple combined typings.
type MapMethodReturnTypes<Type> = {
[Key in keyof Type]: Type[Key] extends ((...args: any) => any) ? ReturnType<Type[Key]> : never;
};
type FilterConverters<Type> = {
[Key in keyof Type]: Key extends `to${string}` ? Type[Key] : never;
};
type Conversions<Type> = PickNonNever<MapMethodReturnTypes<FilterConverters<Type>>>;
interface Person {
name: string;
dob: Date;
toJSON(): object;
toString(): string;
toBinary(): Uint8Array;
}
type PersonConversions = Conversions<Person>;
// this type will be: {toJSON: object, toString: string, toBinary: Uint8Array}
sindresorhus / type-fest
A collection of essential TypeScript types
14.2k
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