isTuple

Checks whether a value is a tuple of a specific structure. A tuple is defined as an array with a fixed length where each element satisfies a corresponding guard.

This helper is fully structural and never throws or mutates input.

Signature

function isTuple<
    const Guards extends readonly ((value: unknown) => boolean)[]
>(
    value: unknown,
    guards: Guards,
): value is {
    [I in keyof Guards]:
        Guards[I] extends (value: unknown) => value is infer T ? T : unknown
}

Parameters

Name	Data type	Description
value	unknown	The value to check. Must be an array of the same length as guards.
guards	Readonly array of guard functions	One guard per tuple position. Each guard must accept unknown and return a boolean or a type predicate.

Returns

A boolean:

• true: If value is an array of the same length as guards and each element passes its corresponding guard.
• false: Otherwise.

Examples

isTuple([1, 'x'], [isNumber, isString] as const);
// → true

isTuple([1, 2], [isNumber, isString] as const);
// → false

isTuple([1], [isNumber, isString] as const);
// → false

Notes

• This helper is structural. It does not rely on TypeScript metadata.
• The guards parameter must be provided as a tuple literal or a const tuple for correct inference.
• Each guard is checked at runtime for safety; non-function guards cause the check to fail.
• Use validateTuple if you need a Result<T> instead of a boolean.

Next up

This is the final topic for structural type guards. In the next section, we'll cover collection-based type guards.

Collections