whenIsOptionalEmpty

Applies a function only when an optional is empty (undefined).

Interactive example

Syntax

Classic signature

function whenIsOptionalEmpty<
  const GenericInput extends unknown,
  const GenericOutput extends AnyValue | EscapeVoid
>(
  input: GenericInput,
  theFunction: (value: Unwrap<Extract<ToEither<GenericInput>, EitherOptionalEmpty>>) => GenericOutput
): GenericOutput | Exclude<ToEither<GenericInput>, EitherOptionalEmpty>;

Curried signature

function whenIsOptionalEmpty<
  const GenericInput extends unknown,
  const GenericOutput extends AnyValue | EscapeVoid
>(
  theFunction: (value: Unwrap<Extract<ToEither<GenericInput>, EitherOptionalEmpty>>) => GenericOutput
): (input: GenericInput) => GenericOutput | Exclude<ToEither<GenericInput>, EitherOptionalEmpty>;

Parameters

• theFunction: Callback executed if the value is undefined.
• input: Value/Either to analyze.

Return value

Result of the callback if empty, otherwise the initial value.

See also

• whenIsOptionalFilled.
• optional.