optional

Wraps an undefined/defined value in an Either, useful for propagating optional fields.

Interactive example

Syntax

function optional<
	const GenericInput extends unknown = undefined
>(
  input: GenericInput
): GenericInput extends undefined
  ? EitherOptionalEmpty
  : EitherOptionalFilled<GenericInput>;

Parameters

• input: Can be undefined or a concrete value.

Return value

• EitherOptionalFilled if the value is defined.
• EitherOptionalEmpty otherwise.

See also

• optionalEmpty.
• optionalFilled.