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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. Markdown · 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 with a plain require()-able CommonJS entry is 2.1.0, published Apr 22, 2019; it declares support for Node.js >=8.

On Node.js 20.19+, 22.12+ and newer, require("array-union") works with the latest version: Node.js loads synchronous ES modules through require(). Verified on Node.js 20, 22, 24 and 26. On Node.js 18, which has no require(esm), require("array-union") fails with ERR_REQUIRE_ESM.

What to do

  1. On Node.js 20.19+, 22.12+ and newer, require("array-union") works with the latest version: Node.js loads synchronous ES modules through require(). Verified on Node.js 20, 22, 24 and 26.
  2. From a CommonJS file, use a dynamic import inside an async function: const arrayUnion = await import("array-union"). That works on every Node.js version the package supports (>=12).
  3. If you need a synchronous require() or run Node.js 18: npm install array-union@2.1.0, the last CommonJS release (published Apr 22, 2019); it declares Node.js >=8.
  4. TypeScript: no types are available for array-union; declare the module yourself if you need them.
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 1.4.0✓ works✓ works

How to import array-union

ES modules (import)

import * as arrayUnion from "array-union";

Namespace import shown because the ESM entry may have no default export; use named imports for what it exports.

CommonJS (require)

// Node.js 20.19+, 22.12+ and newer (verified):
const arrayUnion = require("array-union");

// Any Node.js version the package supports (>=12), from an async function:
async function main() {
  const arrayUnion = await import("array-union");
}

// Or pin the last CommonJS release (declares Node.js >=8):
// 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, corrected where a runtime test of that version contradicted them (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 with a plain require()-able CommonJS entry is 2.1.0, published Apr 22, 2019; it declares support for Node.js >=8.

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

2.1.0 is the last version of array-union with a CommonJS build; it declares Node.js >=8. 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?

From a CommonJS file, use a dynamic import inside an async function: const arrayUnion = await import("array-union"). That works on every Node.js version the package supports (>=12). On Node.js 20.19+, 22.12+ and newer, require("array-union") works with the latest version: Node.js loads synchronous ES modules through require(). Verified on Node.js 20, 22, 24 and 26. Alternatively pin array-union@2.1.0 (declares Node.js >=8).

Does array-union work in Bun?

Yes. import "array-union" loaded successfully in Bun 1.4.0 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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