API reference › @evolu/common › Array › partitionArray

Call Signature

function partitionArray<T, S>(
  array: readonly T[],
  refinement: RefinementWithIndex<T, S>,
): readonly [readonly S[], readonly Exclude<T, S>[]];

Defined in: packages/common/src/Array.ts:572

Partitions an array into two readonly arrays based on a predicate or refinement function.

Returns a tuple where the first array contains elements that satisfy the predicate, and the second array contains elements that do not.

When used with a refinement function (with value is Type syntax), TypeScript will narrow the first array to the narrowed type, making it useful for filtering with Evolu Types like PositiveInt.is.

Example

With predicate

const [evens, odds] = partitionArray([1, 2, 3, 4, 5], (x) => x % 2 === 0);
evens; // [2, 4]
odds; // [1, 3, 5]

With refinement

const mixed: ReadonlyArray<NonEmptyString | PositiveInt> = [
  NonEmptyString.orThrow("hello"),
  PositiveInt.orThrow(42),
];
const [positiveInts, strings] = partitionArray(mixed, PositiveInt.is);
// positiveInts: ReadonlyArray<PositiveInt> (narrowed type)
// strings: ReadonlyArray<NonEmptyString> (Exclude<T, PositiveInt>)

Call Signature

function partitionArray<T>(
  array: readonly T[],
  predicate: PredicateWithIndex<T>,
): readonly [readonly T[], readonly T[]];

Defined in: packages/common/src/Array.ts:577

With predicate.

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