# Is prelude-ls ESM-only? Can you require() it?

> prelude-ls@1.2.1 is a CommonJS package. CommonJS — require() works on every Node.js version we test.

prelude.ls is a functionally oriented utility library. It is powerful and flexible. Almost all of its functions are curried. It is written in, and is the recommended base library for, LiveScript.

Last verified Sep 9, 2026 against prelude-ls@1.2.1.

prelude-ls ships CommonJS only. require("prelude-ls") works on every Node.js version we test (18, 20, 22, 24 and 26) and in Bun. The package declares Node.js >= 0.8.0. import "prelude-ls" 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("prelude-ls") works on every Node.js version we test (18, 20, 22, 24 and 26) and in Bun. The package declares Node.js >= 0.8.0.
2. From ES modules use the default import: import preludeLs from "prelude-ls"; then destructure. Named imports only work when Node.js can statically detect the exports.
3. TypeScript: npm install -D @types/prelude-ls

## Facts

- Latest: 1.2.1 (Apr 2, 2020)
- Module format: CommonJS
- Last CommonJS version: 1.2.1
- TypeScript types: @types/prelude-ls
- Node engines: >= 0.8.0
- Weekly downloads: 101.4M
- License: MIT

## Runtime test results for prelude-ls@1.2.1

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

| Runtime | require("prelude-ls") | import "prelude-ls" |
|---|---|---|
| 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 prelude-ls

ES modules:

```js
import preludeLs from "prelude-ls";
```

CommonJS:

```js
const preludeLs = require("prelude-ls");
```

## Module format by version

Derived from the type, main and exports fields of every stable release on npm (14 versions; the newest 14 shown).

| Versions | Format | First published |
|---|---|---|
| 0.2.0 – 1.2.1 | CommonJS | May 29, 2012 |

## Frequently asked

**Is prelude-ls ESM-only?**

prelude-ls@1.2.1 is a CommonJS package. prelude-ls ships CommonJS only. require("prelude-ls") works on every Node.js version we test (18, 20, 22, 24 and 26) and in Bun. The package declares Node.js >= 0.8.0. import "prelude-ls" 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 prelude-ls with ES module syntax?**

Yes. import preludeLs from "prelude-ls" 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 prelude-ls work in Bun?**

Yes. import "prelude-ls" loaded successfully in Bun 1.4.0 on Sep 9, 2026.

**Does prelude-ls ship TypeScript types?**

Not bundled. Install the community types with "npm install -D @types/prelude-ls".

## Links

- [prelude-ls on npm](https://www.npmjs.com/package/prelude-ls)
- [Source repository](https://github.com/gkz/prelude-ls)
- [HTML version](https://canirequire.com/package/prelude-ls/)
- [JSON version](https://canirequire.com/package/prelude-ls.json)

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