# Is @tootallnate/once ESM-only? Can you require() it?

> @tootallnate/once@3.0.1 is ESM-only. ESM-only since 3.0.0 — last CommonJS version is 2.0.1.

Creates a Promise that waits for a single event

Last verified Sep 9, 2026 against @tootallnate/once@3.0.1.

@tootallnate/once dropped its CommonJS build in 3.0.0 (September 2021). The last version with a plain require()-able CommonJS entry is 2.0.1, published May 3, 2026; it declares support for Node.js >= 10.

On Node.js 20.19+, 22.12+ and newer, require("@tootallnate/once") works with the latest version: Node.js loads synchronous ES modules through require(). Verified on Node.js 20, 22, 24 and 26. On Node.js 18, which has no require(esm), require("@tootallnate/once") fails with ERR_REQUIRE_ESM.

## What to do

1. On Node.js 20.19+, 22.12+ and newer, require("@tootallnate/once") works with the latest version: Node.js loads synchronous ES modules through require(). Verified on Node.js 20, 22, 24 and 26.
2. From a CommonJS file, use a dynamic import inside an async function: const once = await import("@tootallnate/once"). That works on every Node.js version the package supports (>= 10).
3. If you need a synchronous require() or run Node.js 18: npm install @tootallnate/once@2.0.1, the last CommonJS release (published May 3, 2026); it declares Node.js >= 10.
4. TypeScript: types are bundled; install nothing extra.

## Facts

- Latest: 3.0.1 (Feb 9, 2026)
- Module format: ESM-only
- Last CommonJS version: 2.0.1
- ESM-only since: 3.0.0 (Sep 27, 2021)
- TypeScript types: bundled
- Node engines: >= 10
- Weekly downloads: 35.7M
- License: MIT

## Runtime test results for @tootallnate/once@3.0.1

Installed and executed on Sep 9, 2026 with require("@tootallnate/once") from a CommonJS file and import "@tootallnate/once" from an ES module.

| Runtime | require("@tootallnate/once") | import "@tootallnate/once" |
|---|---|---|
| Node.js 18 | fails (ERR_REQUIRE_ESM) | 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 @tootallnate/once

ES modules:

```js
import * as once from "@tootallnate/once";
```

Namespace import shown because the ESM entry may have no default export; use named imports for what it exports.

CommonJS:

```js
// Node.js 20.19+, 22.12+ and newer (verified):
const once = require("@tootallnate/once");

// Any Node.js version the package supports (>= 10), from an async function:
async function main() {
  const once = await import("@tootallnate/once");
}

// Or pin the last CommonJS release (declares Node.js >= 10):
// npm install @tootallnate/once@2.0.1
```

## Module format by version

Derived from the type, main and exports fields of every stable release on npm (8 versions; the newest 8 shown).

| Versions | Format | First published |
|---|---|---|
| 3.0.0 – 3.0.1 | ESM-only | Sep 27, 2021 |
| 1.0.0 – 2.0.1 | CommonJS | Feb 8, 2020 |

## Frequently asked

**Is @tootallnate/once ESM-only?**

@tootallnate/once@3.0.1 is ESM-only. @tootallnate/once dropped its CommonJS build in 3.0.0 (September 2021). The last version with a plain require()-able CommonJS entry is 2.0.1, published May 3, 2026; it declares support for Node.js >= 10.

**Which version of @tootallnate/once still supports CommonJS / require()?**

2.0.1 is the last version of @tootallnate/once with a CommonJS build; it declares Node.js >= 10. Install it with "npm install @tootallnate/once@2.0.1". Every version from 3.0.0 on is ESM-only.

**How do I use @tootallnate/once from a CommonJS file?**

From a CommonJS file, use a dynamic import inside an async function: const once = await import("@tootallnate/once"). That works on every Node.js version the package supports (>= 10). On Node.js 20.19+, 22.12+ and newer, require("@tootallnate/once") works with the latest version: Node.js loads synchronous ES modules through require(). Verified on Node.js 20, 22, 24 and 26. Alternatively pin @tootallnate/once@2.0.1 (declares Node.js >= 10).

**Does @tootallnate/once work in Bun?**

Yes. import "@tootallnate/once" loaded successfully in Bun 1.4.0 on Sep 9, 2026.

**Does @tootallnate/once ship TypeScript types?**

Yes. @tootallnate/once bundles its own type declarations; no @types package is needed.

## Links

- [@tootallnate/once on npm](https://www.npmjs.com/package/@tootallnate/once)
- [Source repository](https://github.com/TooTallNate/once)
- [HTML version](https://canirequire.com/package/@tootallnate/once/)
- [JSON version](https://canirequire.com/package/@tootallnate/once.json)

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