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Is which-collection ESM-only? Can you require() it?

Which kind of Collection (Map, Set, WeakMap, WeakSet) is this JavaScript value? Works cross-realm, without `instanceof`, and despite Symbol.toStringTag.

Last verified Sep 9, 2026 against which-collection@1.0.2. Markdown · JSON

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

which-collection ships CommonJS only. require("which-collection") 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 "which-collection" 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("which-collection") 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 whichCollection from "which-collection"; then destructure. Named imports only work when Node.js can statically detect the exports.
  3. TypeScript: types are bundled; install nothing extra.
Latest
1.0.2 (Mar 8, 2024)
Module format
CommonJS
Last CommonJS version
1.0.2
TypeScript types
Bundled
Node engines
>= 0.4
Weekly downloads
72.3M
License
MIT

Does which-collection@1.0.2 actually load? Runtime test results

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

Runtimerequire("which-collection")import "which-collection"
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 which-collection

ES modules (import)

import whichCollection from "which-collection";

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 whichCollection = require("which-collection");

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 (3 versions; the newest 3 shown).

VersionsFormatFirst published
1.0.0 – 1.0.2CommonJSNov 13, 2019

Frequently asked

Is which-collection ESM-only?

which-collection@1.0.2 is a CommonJS package. which-collection ships CommonJS only. require("which-collection") 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 "which-collection" 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 which-collection with ES module syntax?

Yes. import whichCollection from "which-collection" 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 which-collection work in Bun?

Yes. import "which-collection" loaded successfully in Bun 1.4.0 on Sep 9, 2026.

Does which-collection ship TypeScript types?

Yes. which-collection bundles its own type declarations; no @types package is needed.

Links

Other commonjs packages

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