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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. Markdown · 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 with a plain require()-able CommonJS entry is 3.1.0, published Jul 24, 2020; it declares support for Node.js >=8.

On Node.js 20.19+, 22.12+ and newer, require("mimic-fn") 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("mimic-fn") fails with ERR_REQUIRE_ESM.

What to do

  1. On Node.js 20.19+, 22.12+ and newer, require("mimic-fn") 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 mimicFn = await import("mimic-fn"). 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 mimic-fn@3.1.0, the last CommonJS release (published Jul 24, 2020); it declares Node.js >=8.
  4. TypeScript: types are bundled; install nothing extra.
  5. This package is deprecated: Renamed to mimic-function
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 1.4.0✓ works✓ works

How to import mimic-fn

ES modules (import)

import * as mimicFn from "mimic-fn";

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 mimicFn = require("mimic-fn");

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

// Or pin the last CommonJS release (declares Node.js >=8):
// 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, corrected where a runtime test of that version contradicted them (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 with a plain require()-able CommonJS entry is 3.1.0, published Jul 24, 2020; it declares support for Node.js >=8.

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

3.1.0 is the last version of mimic-fn with a CommonJS build; it declares Node.js >=8. 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?

From a CommonJS file, use a dynamic import inside an async function: const mimicFn = await import("mimic-fn"). That works on every Node.js version the package supports (>=12). On Node.js 20.19+, 22.12+ and newer, require("mimic-fn") works with the latest version: Node.js loads synchronous ES modules through require(). Verified on Node.js 20, 22, 24 and 26. Alternatively pin mimic-fn@3.1.0 (declares Node.js >=8).

Does mimic-fn work in Bun?

Yes. import "mimic-fn" loaded successfully in Bun 1.4.0 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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