[raon0211]

Summary

Adds cartesianProduct to es-toolkit/iterator, the lazy counterpart of the array cartesianProduct, plus a curried form in es-toolkit/fp/iterator.

import { cartesianProduct, range } from 'es-toolkit/iterator';

cartesianProduct([1, 2].values(), ['a', 'b'].values()).toArray();
// => [[1, 'a'], [1, 'b'], [2, 'a'], [2, 'b']]

// The first source is consumed lazily, so it may be infinite.
cartesianProduct(range(0, Infinity), ['a', 'b'].values()).take(3).toArray();
// => [[0, 'a'], [0, 'b'], [1, 'a']]

Design

• Tuples are yielded in lexicographic order (rightmost source advances fastest), matching the array version.
• Every source except the first is traversed many times, so those are buffered into arrays when iteration starts; the first source is consumed one element at a time, allowing an infinite first source (same approach as Rust itertools' cartesian_product).
• Follows the module's IteratorClose protocol: all sources are closed via return when iteration ends or the consumer stops early.
• Edge cases match the array version: no sources → a single empty tuple; any empty source → nothing.

Changes

• src/iterator/cartesianProduct.ts + spec, re-exported from src/iterator/index.ts
• src/fp/iterator/cartesianProduct.ts (curried, cartesianProduct(other)), re-exported from src/fp/iterator/index.ts
• Docs in all 4 languages + added to the iterator intro function lists
• Fixed the stale ENTRYPOINTS list in tests/check-dist.spec.ts, which was missing ./iterator and ./fp/iterator from Phase 1 (feat(iterator): add es-toolkit/iterator lazy iterator module (Phase 1) #1815) and made check-dist fail on main

Test plan

• yarn vitest run src/iterator src/fp/iterator — 102 tests pass
• Full suite yarn vitest run — all pass (including the previously failing check-dist)
• tsc --noEmit, yarn lint — clean

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Project	Deployment	Actions	Updated (UTC)
es-toolkit	Ready	Preview	Aug 17, 2026 8:39am