# Is array.prototype.findlastindex ESM-only? Can you require() it?

> array.prototype.findlastindex@1.2.6 is a CommonJS package. CommonJS — require() works on every Node.js version we test.

An ESnext spec-compliant `Array.prototype.findLastIndex` shim/polyfill/replacement that works as far down as ES3.

Last verified Sep 9, 2026 against array.prototype.findlastindex@1.2.6.

array.prototype.findlastindex ships CommonJS only. require("array.prototype.findlastindex") 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 "array.prototype.findlastindex" 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("array.prototype.findlastindex") 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 arrayPrototypeFindlastindex from "array.prototype.findlastindex"; then destructure. Named imports only work when Node.js can statically detect the exports.
3. TypeScript: no types are available for array.prototype.findlastindex; declare the module yourself if you need them.

## Facts

- Latest: 1.2.6 (Mar 14, 2025)
- Module format: CommonJS
- Last CommonJS version: 1.2.6
- Native ESM since: 1.1.0
- TypeScript types: none
- Node engines: >= 0.4
- Weekly downloads: 37.7M
- License: MIT

## Runtime test results for array.prototype.findlastindex@1.2.6

Installed and executed on Sep 9, 2026 with require("array.prototype.findlastindex") from a CommonJS file and import "array.prototype.findlastindex" from an ES module.

| Runtime | require("array.prototype.findlastindex") | import "array.prototype.findlastindex" |
|---|---|---|
| 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 array.prototype.findlastindex

ES modules:

```js
import arrayPrototypeFindlastindex from "array.prototype.findlastindex";
```

CommonJS:

```js
const arrayPrototypeFindlastindex = require("array.prototype.findlastindex");
```

## Module format by version

Derived from the type, main and exports fields of every stable release on npm (10 versions; the newest 10 shown).

| Versions | Format | First published |
|---|---|---|
| 1.2.5 – 1.2.6 | CommonJS | Mar 19, 2024 |
| 1.1.0 – 1.2.4 | Dual (CommonJS + ESM) | Aug 7, 2021 |
| 1.0.0 | CommonJS | Jul 14, 2021 |

## Frequently asked

**Is array.prototype.findlastindex ESM-only?**

array.prototype.findlastindex@1.2.6 is a CommonJS package. array.prototype.findlastindex ships CommonJS only. require("array.prototype.findlastindex") 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 "array.prototype.findlastindex" 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 array.prototype.findlastindex with ES module syntax?**

Yes. import arrayPrototypeFindlastindex from "array.prototype.findlastindex" 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 array.prototype.findlastindex work in Bun?**

Yes. import "array.prototype.findlastindex" loaded successfully in Bun 1.4.0 on Sep 9, 2026.

**Does array.prototype.findlastindex ship TypeScript types?**

No. array.prototype.findlastindex ships no type declarations and there is no @types package for it.

## Links

- [array.prototype.findlastindex on npm](https://www.npmjs.com/package/array.prototype.findlastindex)
- [Source repository](https://github.com/es-shims/Array.prototype.findLastIndex)
- [HTML version](https://canirequire.com/package/array.prototype.findlastindex/)
- [JSON version](https://canirequire.com/package/array.prototype.findlastindex.json)

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