hasInformation

Type guard based on the literal information stored in the Either. Lets you precisely target one or many business cases without extra introspection.

Interactive example

Syntax

function hasInformation<
  const GenericInput extends unknown,
  GenericInformation extends (
    GenericInput extends Either
      ? ReturnType<typeof informationKind.getValue<GenericInput>>
      : never
  ),
>(
  input: GenericInput,
  information: GenericInformation | GenericInformation[],
): input is Extract<
  GenericInput,
  Kind<typeof informationKind.definition, GenericInformation>
>;

function hasInformation<
  const GenericInput extends unknown,
  GenericInformation extends (
    GenericInput extends Either
      ? ReturnType<typeof informationKind.getValue<GenericInput>>
      : never
  ),
>(
  information: GenericInformation | GenericInformation[],
): (input: GenericInput) => input is Extract<
  GenericInput,
  Kind<typeof informationKind.definition, GenericInformation>
>;

Parameters

• information: Expected literal information, or an array of literal informations.
• input (optional in the curried signature): Value on which to perform the check.

Return value

A boolean, but mostly a type guard: when the result is true, TypeScript knows the Either carries one of the requested informations (Right or Left).

Use cases

• Differentiate several errors/successes within the same Either.
• Match multiple business informations in a single guard.
• Chain with E.whenHasInformation to trigger a targeted action.

See also

• whenHasInformation – Variant with callback.
• right / left – Constructors that enforce this literal information.