castMaxElements

The castMaxElements() function readapts an existing MaxElements constraint to a less restrictive maximum without checking the array again at runtime. It is useful when the new maximum is already induced by the constraints carried by the array: for example, a MaxElements<10> array is compatible with MaxElements<15>.

Interactive example

Syntax

Classic signature

function castMaxElements<
	GenericArray extends readonly unknown[] & MaxElements<number>,
	GenericLength extends number
>(
	array: GenericArray,
	maxLength: GenericLength
): GenericArray & MaxElements<GenericLength>

Curried signature

function castMaxElements<
	GenericArray extends readonly unknown[] & MaxElements<number>,
	GenericLength extends number
>(
	maxLength: GenericLength
): (array: GenericArray) => GenericArray & MaxElements<GenericLength>

Parameters

• array: Array that already carries a MaxElements constraint.
• maxLength: New literal maximum to add to the type. It must be greater than or equal to the already known maximum.

Return value

The same array, with an additional MaxElements<maxLength> type marker.

The function does not validate the length at runtime. Use maxElements first to obtain the initial constraint.

See also

• maxElements - Checks and creates a MaxElements constraint
• minElements - Checks a minimum number of elements