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Is mimic-fn ESM-only? Can you require() it?

Make a function mimic another one

Last verified Sep 9, 2026 against mimic-fn@5.0.0. JSON

ESM-only ESM-only since 4.0.0 — last CommonJS version is 3.1.0

mimic-fn dropped its CommonJS build in 4.0.0 (April 2021). The last version you can require() on every Node.js version, including 18 and older, is 3.1.0, published Jul 24, 2020.

On Node.js 20.19+, 22.12+ and every newer release, require("mimic-fn") 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
5.0.0 (Nov 5, 2023)
Module format
ESM-only
Last CommonJS version
3.1.0
ESM-only since
4.0.0 (Apr 7, 2021)
TypeScript types
Bundled
Node engines
>=12
Weekly downloads
99.7M
License
MIT

Deprecated: Renamed to mimic-function

Does mimic-fn@5.0.0 actually load? Runtime test results

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

Runtimerequire("mimic-fn")import "mimic-fn"
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 mimic-fn

ES modules (import)

import mimicFn from "mimic-fn";

CommonJS (require)

// Node.js 20.19+ / 22.12+ / newer (package has no top-level await):
const mimicFn = require("mimic-fn");

// Any Node.js version:
const mimicFn = await import("mimic-fn");

// Or pin the last CommonJS release:
// npm install mimic-fn@3.1.0

Module format by version

Derived from the type, main and exports fields of every stable release on npm (9 versions; the newest 9 shown).

VersionsFormatFirst published
4.0.0 – 5.0.0ESM-onlyApr 7, 2021
1.0.0 – 3.1.0CommonJSOct 19, 2016

Frequently asked

Is mimic-fn ESM-only?

mimic-fn@5.0.0 is ESM-only. mimic-fn dropped its CommonJS build in 4.0.0 (April 2021). The last version you can require() on every Node.js version, including 18 and older, is 3.1.0, published Jul 24, 2020.

Which version of mimic-fn still supports CommonJS / require()?

3.1.0 is the last version of mimic-fn with a CommonJS build. Install it with "npm install mimic-fn@3.1.0". Every version from 4.0.0 on is ESM-only.

How do I use mimic-fn from a CommonJS file?

Use a dynamic import: const mod = await import("mimic-fn"). On Node.js 20.19+, 22.12+ and newer, a plain require("mimic-fn") also works for ESM packages that do not use top-level await. Alternatively pin mimic-fn@3.1.0.

Does mimic-fn work in Bun?

Yes. import "mimic-fn" loaded successfully in Bun 1.4 on Sep 9, 2026.

Does mimic-fn ship TypeScript types?

Yes. mimic-fn bundles its own type declarations; no @types package is needed.

Links

Other esm-only packages

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