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Is array-union ESM-only? Can you require() it?

Create an array of unique values, in order, from the input arrays

Last verified Sep 9, 2026 against array-union@3.0.1. JSON

ESM-only ESM-only since 3.0.0 — last CommonJS version is 2.1.0

array-union dropped its CommonJS build in 3.0.0 (March 2021). The last version you can require() on every Node.js version, including 18 and older, is 2.1.0, published Apr 22, 2019.

On Node.js 20.19+, 22.12+ and every newer release, require("array-union") works anyway: Node can load synchronous ES modules through require(). Verified on Node 20, 22, 24, 26. Node.js 18 and older still fail with ERR_REQUIRE_ESM.

Latest
3.0.1 (Mar 1, 2021)
Module format
ESM-only
Last CommonJS version
2.1.0
ESM-only since
3.0.0 (Mar 1, 2021)
TypeScript types
None
Node engines
>=12
Weekly downloads
31.3M
License
MIT

Does array-union@3.0.1 actually load? Runtime test results

Installed and executed on Sep 9, 2026 with require("array-union") from a CommonJS file and import "array-union" from an ES module.

Runtimerequire("array-union")import "array-union"
Node.js 18✗ failsERR_REQUIRE_ESM✓ works
Node.js 20✓ works✓ works
Node.js 22✓ works✓ works
Node.js 24✓ works✓ works
Node.js 26✓ works✓ works
Bun 1.4✓ works✓ works

How to import array-union

ES modules (import)

import arrayUnion from "array-union";

CommonJS (require)

// Node.js 20.19+ / 22.12+ / newer (package has no top-level await):
const arrayUnion = require("array-union");

// Any Node.js version:
const arrayUnion = await import("array-union");

// Or pin the last CommonJS release:
// npm install array-union@2.1.0

Module format by version

Derived from the type, main and exports fields of every stable release on npm (8 versions; the newest 8 shown).

VersionsFormatFirst published
3.0.0 – 3.0.1ESM-onlyMar 1, 2021
0.1.0 – 2.1.0CommonJSJun 19, 2014

Frequently asked

Is array-union ESM-only?

array-union@3.0.1 is ESM-only. array-union dropped its CommonJS build in 3.0.0 (March 2021). The last version you can require() on every Node.js version, including 18 and older, is 2.1.0, published Apr 22, 2019.

Which version of array-union still supports CommonJS / require()?

2.1.0 is the last version of array-union with a CommonJS build. Install it with "npm install array-union@2.1.0". Every version from 3.0.0 on is ESM-only.

How do I use array-union from a CommonJS file?

Use a dynamic import: const mod = await import("array-union"). On Node.js 20.19+, 22.12+ and newer, a plain require("array-union") also works for ESM packages that do not use top-level await. Alternatively pin array-union@2.1.0.

Does array-union work in Bun?

Yes. import "array-union" loaded successfully in Bun 1.4 on Sep 9, 2026.

Does array-union ship TypeScript types?

No. array-union ships no type declarations and there is no @types package for it.

Links

Other esm-only packages

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