whenNot

The whenNot() function applies a transformation only when the predicate fails (or when the type guard does not match). Otherwise, the input is returned as is. Exists in immediate and curried versions.

Interactive example

Syntax

Classic signatures

// Type Guard predicate
function whenNot<
	GenericInput extends AnyValue,
	GenericPredicatedInput extends GenericInput,
	GenericOutput extends AnyValue | EscapeVoid
>(
	input: GenericInput,
	ifFunction: (input: GenericInput) => input is GenericPredicatedInput,
	theFunction: (predicatedInput: Exclude<GenericInput, GenericPredicatedInput>) => GenericOutput
): GenericOutput | GenericPredicatedInput;

// Boolean predicate
function whenNot<
	GenericInput extends AnyValue,
	GenericOutput extends AnyValue | EscapeVoid
>(
	input: GenericInput,
	ifFunction: (input: GenericInput) => boolean,
	theFunction: (predicatedInput: GenericInput) => GenericOutput
): GenericOutput | GenericInput;

Curried signatures

// Type Guard predicate
function whenNot<
	GenericInput extends AnyValue,
	GenericPredicatedInput extends GenericInput,
	GenericOutput extends AnyValue | EscapeVoid
>(
	ifFunction: (input: GenericInput) => input is GenericPredicatedInput,
	theFunction: (predicatedInput: Exclude<GenericInput, GenericPredicatedInput>) => GenericOutput
): (
	input: GenericInput
) => GenericOutput | BreakGenericLink<GenericPredicatedInput>;

// Boolean predicate
function whenNot<
	GenericInput extends AnyValue,
	GenericOutput extends AnyValue | EscapeVoid
>(
	ifFunction: (input: GenericInput) => boolean,
	theFunction: (predicatedInput: GenericInput) => GenericOutput
): (
	input: GenericInput
) => GenericOutput | GenericInput;

Parameters

• input : The value to test (optional in curried mode).
• ifFunction : Function that decides whether or not to skip the transformation (can be a type guard).
• theFunction : Function executed only if the predicate fails.

Return value

If the predicate fails, returns the result of theFunction. Otherwise, returns the input unchanged.

See also

• when - Inverse version
• whenElse - Two explicit branches