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Is is-async-function ESM-only? Can you require() it?

Determine if a function is a native async function.

Last verified Sep 9, 2026 against is-async-function@2.1.1. Markdown · JSON

CommonJS CommonJS — require() works on every Node.js version we test

is-async-function ships CommonJS only. require("is-async-function") works on every Node.js version we test (18, 20, 22, 24 and 26) and in Bun. The package declares Node.js >= 0.4. import "is-async-function" also works because Node.js and Bun can import CommonJS from ES modules, but only the default export is guaranteed; named imports depend on Node's static analysis of the module.

What to do

  1. require("is-async-function") works on every Node.js version we test (18, 20, 22, 24 and 26) and in Bun. The package declares Node.js >= 0.4.
  2. From ES modules use the default import: import isAsyncFunction from "is-async-function"; then destructure. Named imports only work when Node.js can statically detect the exports.
  3. TypeScript: types are bundled; install nothing extra.
Latest
2.1.1 (Jan 23, 2025)
Module format
CommonJS
Last CommonJS version
2.1.1
TypeScript types
Bundled
Node engines
>= 0.4
Weekly downloads
68.5M
License
MIT

Does is-async-function@2.1.1 actually load? Runtime test results

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

Runtimerequire("is-async-function")import "is-async-function"
Node.js 18✓ works✓ 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 is-async-function

ES modules (import)

import isAsyncFunction from "is-async-function";

Named imports from a CommonJS package only work when Node.js can statically detect them. If a named import fails, use the default import and destructure.

CommonJS (require)

const isAsyncFunction = require("is-async-function");

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 (17 versions; the newest 17 shown).

VersionsFormatFirst published
0.0.0 – 2.1.1CommonJSJun 5, 2015

Frequently asked

Is is-async-function ESM-only?

is-async-function@2.1.1 is a CommonJS package. is-async-function ships CommonJS only. require("is-async-function") works on every Node.js version we test (18, 20, 22, 24 and 26) and in Bun. The package declares Node.js >= 0.4. import "is-async-function" also works because Node.js and Bun can import CommonJS from ES modules, but only the default export is guaranteed; named imports depend on Node's static analysis of the module.

Can I import is-async-function with ES module syntax?

Yes. import isAsyncFunction from "is-async-function" works in Node.js and Bun because they support importing CommonJS modules. Named imports work only when Node.js can statically detect the exports.

Does is-async-function work in Bun?

Yes. import "is-async-function" loaded successfully in Bun 1.4.0 on Sep 9, 2026.

Does is-async-function ship TypeScript types?

Yes. is-async-function bundles its own type declarations; no @types package is needed.

Links

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