hasInformation

Type guard based on the literal information stored in the Either. Lets you precisely target a business case without extra introspection.

Interactive example

Syntax

function hasInformation<
  const GenericInput extends unknown,
  GenericInformation extends ReturnType<typeof eitherInformationKind.getValue<GenericInput>>
>(
  input: GenericInput,
  information: GenericInformation
): input is Extract<GenericInput, Kind<typeof eitherInformationKind.definition, GenericInformation>>;

function hasInformation<
  const GenericInput extends unknown,
  GenericInformation extends ReturnType<typeof eitherInformationKind.getValue<GenericInput>>
>(
  information: GenericInformation
): (input: GenericInput) => input is Extract<GenericInput, Kind<typeof eitherInformationKind.definition, GenericInformation>>;

Parameters

• information: Expected literal string ("user.created", "user.invalid", etc.).
• 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 the requested information (Right or Left).

Use cases

• Differentiate several errors/successes within the same Either.
• Simplify switch/case by relying on literals.
• Chain with E.whenHasInformation to trigger a targeted action.

See also

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