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Is onetime ESM-only? Can you require() it?

Ensure a function is only called once

Last verified Sep 9, 2026 against onetime@8.0.0. Markdown · JSON

ESM-only ESM-only since 6.0.0 — last CommonJS version is 5.1.2

onetime dropped its CommonJS build in 6.0.0 (April 2021). The last version with a plain require()-able CommonJS entry is 5.1.2, published Aug 9, 2020; it declares support for Node.js >=6.

On Node.js 22.12+ and newer (onetime@8.0.0 declares Node.js >=22), require("onetime") works with the latest version: Node.js loads synchronous ES modules through require(). Verified on Node.js 22, 24 and 26. Node.js 18 has no require(esm), and onetime@8.0.0 declares Node.js >=22, so 18 is outside its supported range anyway.

onetime@8.0.0 declares engines ">=22", so Node.js 18, 20 are outside its supported range regardless of module format.

What to do

  1. On Node.js 22.12+ and newer (onetime@8.0.0 declares Node.js >=22), require("onetime") works with the latest version: Node.js loads synchronous ES modules through require(). Verified on Node.js 22, 24 and 26.
  2. From a CommonJS file, use a dynamic import inside an async function: const onetime = await import("onetime"). That works on every Node.js version the package supports (>=22).
  3. If you need a synchronous require() or run Node.js 18: npm install onetime@5.1.2, the last CommonJS release (published Aug 9, 2020); it declares Node.js >=6.
  4. onetime@8.0.0 declares engines ">=22", so Node.js 18, 20 are unsupported regardless: upgrade Node.js or pin an older release.
  5. TypeScript: types are bundled; install nothing extra.
Latest
8.0.0 (Feb 2, 2026)
Module format
ESM-only
Last CommonJS version
5.1.2
ESM-only since
6.0.0 (Apr 8, 2021)
TypeScript types
Bundled
Node engines
>=22
Weekly downloads
162.3M
License
MIT

Does onetime@8.0.0 actually load? Runtime test results

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

Runtimerequire("onetime")import "onetime"
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 onetime

ES modules (import)

import * as onetime from "onetime";

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

CommonJS (require)

// Node.js 22.12+ and newer (verified):
const onetime = require("onetime");

// Any Node.js version the package supports (>=22), from an async function:
async function main() {
  const onetime = await import("onetime");
}

// Or pin the last CommonJS release (declares Node.js >=6):
// npm install onetime@5.1.2

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 (15 versions; the newest 15 shown).

VersionsFormatFirst published
6.0.0 – 8.0.0ESM-onlyApr 8, 2021
0.1.0 – 5.1.2CommonJSDec 13, 2013

Frequently asked

Is onetime ESM-only?

onetime@8.0.0 is ESM-only. onetime dropped its CommonJS build in 6.0.0 (April 2021). The last version with a plain require()-able CommonJS entry is 5.1.2, published Aug 9, 2020; it declares support for Node.js >=6.

Which version of onetime still supports CommonJS / require()?

5.1.2 is the last version of onetime with a CommonJS build; it declares Node.js >=6. Install it with "npm install onetime@5.1.2". Every version from 6.0.0 on is ESM-only.

How do I use onetime from a CommonJS file?

From a CommonJS file, use a dynamic import inside an async function: const onetime = await import("onetime"). That works on every Node.js version the package supports (>=22). On Node.js 22.12+ and newer (onetime@8.0.0 declares Node.js >=22), require("onetime") works with the latest version: Node.js loads synchronous ES modules through require(). Verified on Node.js 22, 24 and 26. Alternatively pin onetime@5.1.2 (declares Node.js >=6).

Does onetime work in Bun?

Yes. import "onetime" loaded successfully in Bun 1.4.0 on Sep 9, 2026.

Does onetime ship TypeScript types?

Yes. onetime bundles its own type declarations; no @types package is needed.

Links

Other esm-only packages

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