instanceOf

The instanceOf() function creates a type guard based on one or several constructors. It checks instanceof while keeping precise typing.

Interactive example

Syntax

Classic signature

function instanceOf<
	GenericInput extends unknown,
	GenericConstructor extends AnyConstructor
>(
	input: GenericInput,
	constructor: GenericConstructor | GenericConstructor[]
): input is Extract<GenericInput, InstanceType<GenericConstructor>>;

Curried signature

function instanceOf<
	GenericInput extends unknown,
	GenericConstructor extends AnyConstructor
>(
	constructor: GenericConstructor | GenericConstructor[]
): (input: GenericInput) => input is Extract<GenericInput, InstanceType<GenericConstructor>>;

Parameters

• constructor : Constructor or array of accepted constructors.
• input (direct overload) : Tested value.

Return value

A type guard that is true when input is an instance of one of the constructors.

See also

• isType - Checks a generic runtime type
• equal - Comparison to literals