API Reference > bentleyjs-core > Collections > partitionArray

partitionArray Function

Partitions an array in-place according to some criterion, such that elements that fulfill the criterion are grouped in the lower

portion of the array, and those that fail to fulfill the criterion are grouped in the upper portion of the array.

partitionArray<T>(array: T[], criterion: (element: T) => boolean): number

note The relative ordering of elements within each partition is unspecified. Example:

function isEven(n: number) { return 0 === n % 2; }
const list = [ 1, 2, 3, 4, 5 ];
const firstOddIndex = partitionArray(list, isEven); // firstOddIndex = 2
// 2 and 4 now appear before 1, 3, and 5 in the list; their ordering is otherwise unspecified.
for (let i = 0; i < list.length; i++)
  assert(isEven(list[i]) === i < firstOddIndex);
Parameter Type Description
array T[] The array to be partitioned.
criterion (element: T) => boolean A function invoked for each element of the array, returning whether the element fulfills the criterion.

Returns - number

The index of the upper partition, i.e., of the first element that fails the criterion. If all elements fulfill the criterion, this is the length of the array.

Defined in

Last Updated: 12 June, 2024