addToSet - API reference

API reference › @evolu/common › Set › addToSet

function addToSet<T>(set: ReadonlySet<T>, item: T): NonEmptyReadonlySet<T>;

Defined in: packages/common/src/Set.ts:165

Returns a new readonly set with an item added.

If the item already exists, returns a new set with the same elements (still a new reference for change detection).

Adding without mutation

import {
  addToSet,
  assertEqual,
  assertTrue,
  assertType,
  type NonEmptyReadonlySet,
} from "@evolu/common";

const original: ReadonlySet<number> = new Set([1, 2]);
const added = addToSet(original, 3);
const unchanged = addToSet(original, 2);

assertType<NonEmptyReadonlySet<number>, typeof added>();
assertEqual(added, new Set([1, 2, 3]));
assertTrue(unchanged !== original);