isType

The isType() function creates a type guard based on typeof, Array.isArray, iterables, functions, etc. It allows narrowing a union to the checked type.

Interactive example

Syntax

Classic signature

function isType<
	GenericInput extends unknown,
	GenericType extends EligibleType<GenericInput>
>(
	input: GenericInput,
	type: GenericType
): input is ComputeResult<GenericInput, Type[GenericType]>;

Curried signature

function isType<
	GenericInput extends unknown,
	GenericType extends EligibleType<GenericInput>
>(
	type: GenericType
): (input: GenericInput) => input is ComputeResult<GenericInput, Type[GenericType]>;

Parameters

• type : The runtime type to check.
• input (direct overload) : Tested value.

Return value

A boolean acting as a type guard by narrowing the union to the requested type.

See also

• instanceOf - Checks via a constructor
• equal - Comparison to literals