API reference › @evolu/common › Array › filterArray

Call Signature

function filterArray<T, S>(
  array: readonly T[],
  refinement: (item: T, index: number, array: readonly T[]) => item is S,
): readonly S[];

Defined in: packages/common/src/Array.ts:639

Filters an array using a predicate or refinement function, returning a new readonly array.

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

With predicate

import { assertEqual, filterArray } from "@evolu/common";

const evens = filterArray([1, 2, 3, 4, 5], (x) => x % 2 === 0);
assertEqual(evens, [2, 4]);

With refinement

import {
  assertEqual,
  assertType,
  filterArray,
  NonEmptyTrimmedString,
  PositiveInt,
} from "@evolu/common";

const mixed: ReadonlyArray<NonEmptyTrimmedString | PositiveInt> = [
  NonEmptyTrimmedString.orThrow("hello"),
  PositiveInt.orThrow(42),
];
const positiveInts = filterArray(mixed, PositiveInt.is);
assertEqual(positiveInts, [42]);
assertType<ReadonlyArray<PositiveInt>, typeof positiveInts>();

The predicate receives (item, index, array), matching native Array.filter.

Call Signature

function filterArray<T>(
  array: readonly T[],
  predicate: (item: T, index: number, array: readonly T[]) => boolean,
): readonly T[];

Defined in: packages/common/src/Array.ts:644

With predicate.

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