Value

The @perfective/value package provides functions to work with undefined and null values and utility types (similar to the TS NonNullable<T> to describe some of such values.

• Utility types:
  • type Defined<T> = T extends undefined ? never : T;
  • type Undefined<T> = T extends undefined ? T : never;
  • type NotNull<T> = T extends null ? never : T;
  • type Null<T> = T extends null ? T : never;
  • type Present<T> = T extends null | undefined ? never : T — same as NonNullable<T>, but is used in the project for consistency with the type guards;
  • type Absent<T> = T extends null | undefined ? T : never.
• Type Guards:
  • isDefined<T>(value: T | undefined): value is T;
  • isUndefined<T>(value: T | undefined): value is undefined;
  • isNotNull<T>(value: T | null): value is T;
  • isNull<T>(value: T | null): value is null;
  • isPresent<T>(value: T | null | undefined): value is T;
  • isAbsent<T>(value: T | null | undefined): value is null | undefined.
• typeof types and functions:
  • EcmaType — is one of undefined, boolean, number, bigint, string, symbol, function, or object.
  • TsType — is one of EcmaType or null, array, and unknown.
  • TypeOf<T> — a conditional type that returns TsType dynamically.
  • typeOf<T>(value: T | null | undefined): TypeOf<T> & TsType.
  • isTypeOf<T>(type: TypeOf): (value: T | null | undefined) => boolean;
  • isNotTypeOf<T>(type: TypeOf): (value: T | null | undefined) => boolean.
• Handling void:
  • voidable<T>(value: T | void): T | null | undefined.

Full documentation is available in the repository.