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# es-toolkit &middot; [![MIT License](https://img.shields.io/badge/license-MIT-blue.svg)](https://github.com/toss/slash/blob/main/LICENSE) [![codecov](https://codecov.io/gh/toss/es-toolkit/graph/badge.svg?token=8N5S3AR3C7)](https://codecov.io/gh/toss/es-toolkit) [![NPM badge](https://img.shields.io/npm/v/es-toolkit?logo=npm)](https://www.npmjs.com/package/es-toolkit) [![JSR badge](https://jsr.io/badges/@es-toolkit/es-toolkit)](https://jsr.io/@es-toolkit/es-toolkit) [![Discord Badge](https://discord.com/api/guilds/1281071127052943361/widget.png?style=shield)](https://discord.gg/vGXbVjP2nY)

English | [한국어](https://github.com/toss/es-toolkit/blob/main/README-ko_kr.md) | [简体中文](https://github.com/toss/es-toolkit/blob/main/README-zh_hans.md) | [日本語](https://github.com/toss/es-toolkit/blob/main/README-ja_jp.md)

es-toolkit is a state-of-the-art, high-performance JavaScript utility library with a small bundle size and strong type annotations.

- es-toolkit offers a variety of everyday utility functions with modern implementations, such as [debounce](https://es-toolkit.dev/reference/function/debounce.html), [delay](https://es-toolkit.dev/reference/promise/delay.html), [chunk](https://es-toolkit.dev/reference/array/chunk.html), [sum](https://es-toolkit.dev/reference/math/sum.html), and [pick](https://es-toolkit.dev/reference/object/pick.html).
- Designed with performance in mind, es-toolkit achieves [2-3× better performance](https://es-toolkit.dev/performance.html) in modern JavaScript environments.
- es-toolkit supports tree shaking out of the box, and [reduces JavaScript code by up to 97%](https://es-toolkit.dev/bundle-size.html) compared to other libraries.
- es-toolkit offers a complete compatibility layer to seamlessly replace lodash, available as [es-toolkit/compat](https://es-toolkit.dev/compatibility.html).
- es-toolkit includes built-in TypeScript support, with straightforward yet robust types. It also provides useful type guards such as [isNotNil](https://es-toolkit.dev/reference/predicate/isNotNil.html).
- es-toolkit is trusted and used by popular open-source projects like [Storybook](https://github.com/storybookjs/storybook/blob/9d862798d666678cc4822e857c00bbd744169ced/code/core/package.json#L358), [Recharts](https://github.com/recharts/recharts/blob/0fa4cc325da403b6fa1c6be0f820896ed92f806a/package.json#L94), [ink](https://github.com/vadimdemedes/ink/blob/2090ad9779be59dea71d173eb49785b7bd4495d0/package.json#L55), and [CKEditor](https://github.com/ckeditor/ckeditor5/blob/60d5fac804643cb4d359767ee2f94e3d92d1fcc5/packages/ckeditor5-core/package.json#L53).
- es-toolkit is battle-tested with 100% test coverage, ensuring reliability and robustness.

## Examples

```tsx
// import from '@es-toolkit/es-toolkit' in jsr.
import { chunk, debounce } from 'es-toolkit';

const debouncedLog = debounce(message => {
  console.log(message);
}, 300);

// This call will be debounced
debouncedLog('Hello, world!');

const array = [1, 2, 3, 4, 5, 6];
const chunkedArray = chunk(array, 2);

console.log(chunkedArray);
// Output: [[1, 2], [3, 4], [5, 6]]
```

## AI Integration

es-toolkit provides [Agent Skills](https://skills.sh) for AI coding tools like Claude Code, Cursor, and Copilot.

```bash
npx skills add toss/es-toolkit
```

For Claude Code, you can also install via the plugin marketplace:

```
/plugin marketplace add toss/es-toolkit
/plugin install es-toolkit@es-toolkit-plugin
```

For more details, see the [AI Integration guide](https://es-toolkit.dev/ai-integration.html).

## Contributing

We welcome contribution from everyone in the community. Read below for detailed contribution guide.

[CONTRIBUTING](https://github.com/toss/es-toolkit/blob/main/.github/CONTRIBUTING.md)

## License

MIT © Viva Republica, Inc. See [LICENSE](./LICENSE) for details.

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