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

> which-collection@1.0.2 is a CommonJS package. CommonJS — require() works on every Node.js version we test.

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.

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.

## Facts

- 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

## Runtime test results for which-collection@1.0.2

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

| Runtime | require("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:

```js
import whichCollection from "which-collection";
```

CommonJS:

```js
const whichCollection = require("which-collection");
```

## Module format by version

Derived from the type, main and exports fields of every stable release on npm (3 versions; the newest 3 shown).

| Versions | Format | First published |
|---|---|---|
| 1.0.0 – 1.0.2 | CommonJS | Nov 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

- [which-collection on npm](https://www.npmjs.com/package/which-collection)
- [Source repository](https://github.com/inspect-js/which-collection)
- [HTML version](https://canirequire.com/package/which-collection/)
- [JSON version](https://canirequire.com/package/which-collection.json)

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