# thenify-ex

> Promisify a callback-based function

Latest version **4.4.0** (published 2025-01-30) · MIT license · 0 weekly downloads

## Install

```sh
npm install thenify-ex
pnpm add thenify-ex
yarn add thenify-ex
bun add thenify-ex
```

## Health

**Score 40/100 (D)** — status: maintenance-mode.

Positive: has types; esm support; no vulnerabilities; high quality score.

Warnings: low downloads.

Negative: stale; low maintenance score.

## Facts

| | |
|---|---|
| Version | 4.4.0 |
| Published | 2025-01-30 |
| First published | 2025-01-26 |
| Weekly downloads | 0 |
| License | MIT |
| TypeScript types | bundled |
| Module format | ESM + CommonJS |
| Dependencies | 0 |
| Unpacked size | 19.7 KB |
| Known vulnerabilities | 0 |
| Install scripts | no |
| Maintainers | erossignon |
| Keywords | promisify, promise, thenify, then, es6 |

## Links

- npm: https://www.npmjs.com/package/thenify-ex
- Repository: https://github.com/node-opcua/thenify-ex
- Homepage: https://github.com/node-opcua/thenify-ex#readme
- Issues: https://github.com/node-opcua/thenify-ex/issues
- npm.io page: https://npm.io/package/thenify-ex

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## Recent versions

- 4.4.0 (latest) — 2025-01-30
- 4.3.0 — 2025-01-30
- 4.2.0 — 2025-01-26
- 4.1.0 — 2025-01-26
- 4.0.0 — 2025-01-26

## README

# thenify-ex

A  fork of [thenify](thenify-url) to support modern CJS/ESM modules with typescript support.



[![NPM version][npm-image]][npm-url]
[![Build status][github-action-image]][github-action-url]
[![Test coverage][coveralls-image]][coveralls-url]
[![License][license-image]][license-url]
[![Downloads][downloads-image]][downloads-url]

Promisify a callback-based function using [`any-promise`](https://github.com/kevinbeaty/any-promise).

- Preserves function names
- Uses a native promise implementation if available and tries to fall back to a promise implementation such as `bluebird`
- Converts multiple arguments from the callback into an `Array`, also support change the behavior by `options.multiArgs`
- Resulting function never deoptimizes
- Supports both callback and promise style

An added benefit is that `throw`n errors in that async function will be caught by the promise!

## API

### fn = thenify(fn, options)


Promisifies a function.

### Options

`options` are optional.

- `options.withCallback` - support both callback and promise style, default to `false`.
- `options.multiArgs` - change the behavior when callback have multiple arguments. default to `true`.

  - `true` - converts multiple arguments to an array
  - `false`- always use the first argument
  - `Array` - converts multiple arguments to an object with keys provided in `options.multiArgs`

- Turn async functions into promises


```js
import { thenify } from 'thenify';

const  somethingAsync = thenify(function somethingAsync(a, b, c, callback) {
  callback(null, a, b, c)
})
```

- Backward compatible with callback

```js
import { thenify } from 'thenify';

const somethingAsync = thenify(
  function somethingAsync(a, b, c, callback) {
    callback(null, a, b, c)
  },
  { withCallback: true },
)

// somethingAsync(a, b, c).then(onFulfilled).catch(onRejected);
// somethingAsync(a, b, c, function () {});
```

or use `withCallback()`

```js
import { withCallback}  from "thenify";

var somethingAsync = withCallback(function somethingAsync(a, b, c, callback) {
  callback(null, a, b, c)
})

// somethingAsync(a, b, c).then(onFulfilled).catch(onRejected);
// somethingAsync(a, b, c, function () {});
```

- Always return the first argument in callback

```js
import { thenify}  from "thenify";

var promise = thenify(
  function (callback) {
    callback(null, 1, 2, 3)
  },
  { multiArgs: false },
)

// promise().then(function onFulfilled(value) {
//   assert.equal(value, 1);
// });
```

- Converts callback arguments to an object

```js
import { thenify}  from "thenify";

var promise = thenify(
  function (callback) {
    callback(null, 1, 2, 3)
  },
  { multiArgs: ['one', 'tow', 'three'] },
)

// promise().then(function onFulfilled(value) {
//   assert.deepEqual(value, {
//     one: 1,
//     tow: 2,
//     three: 3
//   });
// });
```

[github-action-image]: https://github.com/node-opcua/thenify2/actions/workflows/workflow.yaml/badge.svg
[github-action-url]: https://github.com/node-opcua/thenify2/actions
[gitter-image]: https://badges.gitter.im/thenables/thenify.png
[gitter-url]: https://gitter.im/thenables/thenify
[npm-image]: https://img.shields.io/npm/v/thenify.svg?style=flat-square
[npm-url]: https://npmjs.org/package/thenify
[github-tag]: http://img.shields.io/github/tag/thenables/thenify.svg?style=flat-square
[github-url]: https://github.com/thenables/thenify/tags
[coveralls-image]: https://img.shields.io/coveralls/thenables/thenify.svg?style=flat-square
[coveralls-url]: https://coveralls.io/r/thenables/thenify
[david-image]: http://img.shields.io/david/thenables/thenify.svg?style=flat-square
[david-url]: https://david-dm.org/thenables/thenify
[license-image]: http://img.shields.io/npm/l/thenify.svg?style=flat-square
[license-url]: LICENSE
[downloads-image]: http://img.shields.io/npm/dm/thenify-ex.svg?style=flat-square
[downloads-url]: https://npmjs.org/package/thenify-ex

---
_Source: https://npm.io/package/thenify-ex · Machine-readable twin of the npm.io package page. Health data is recomputed on every publish._