# frequency-set

> A set that keeps the frequency of occurrences.

Latest version **2.1.0** (published 2025-10-17) · MIT license · 0 weekly downloads

## Install

```sh
npm install frequency-set
pnpm add frequency-set
yarn add frequency-set
bun add frequency-set
```

## Health

**Score 60/100 (C)** — status: stable.

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

Warnings: low downloads.

## Facts

| | |
|---|---|
| Version | 2.1.0 |
| Published | 2025-10-17 |
| First published | 2020-09-22 |
| Weekly downloads | 0 |
| License | MIT |
| TypeScript types | bundled |
| Module format | ESM + CommonJS |
| Dependencies | 0 |
| Unpacked size | 11.8 KB |
| Known vulnerabilities | 0 |
| Install scripts | no |
| GitHub stars | 3 |
| Author | GENTILHOMME Thomas |
| Maintainers | fraxken |
| Keywords | set, frequency, count, map |

## Links

- npm: https://www.npmjs.com/package/frequency-set
- Repository: https://github.com/fraxken/FrequencySet
- Homepage: https://github.com/fraxken/FrequencySet#readme
- Issues: https://github.com/fraxken/FrequencySet/issues
- npm.io page: https://npm.io/package/frequency-set

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## Recent versions

- 2.1.0 (latest) — 2025-10-17
- 2.0.1 — 2025-10-17
- 2.0.0 — 2025-10-05
- 1.0.2 — 2022-09-03
- 1.0.1 — 2020-09-22
- 1.0.0 — 2020-09-22

## README

<p align="center"><h1 align="center">
  FrequencySet
</h1>

<p align="center">
  An ES6 Set compliant structure that keeps the frequency of occurrences.
</p>

<p align="center">
    <a href="https://github.com/fraxken/FrequencySet">
        <img src="https://img.shields.io/badge/dynamic/json.svg?url=https://raw.githubusercontent.com/fraxken/FrequencySet/master/package.json&query=$.version&label=Version">
    </a>
    <a href="https://github.com/fraxken/FrequencySet">
        <img src="https://img.shields.io/badge/Maintained%3F-yes-green.svg" alt="maintenance">
    </a>
    <a href="https://github.com/fraxken/FrequencySet">
        <img src="https://img.shields.io/github/license/mashape/apistatus.svg" alt="license">
    </a>
</p>

## Requirements
- [Node.js](https://nodejs.org/en/) v22 or higher

## Getting Started

This package is available in the Node Package Repository and can be easily installed with [npm](https://docs.npmjs.com/getting-started/what-is-npm) or [yarn](https://yarnpkg.com).

```bash
$ npm i frequency-set
# or
$ yarn add frequency-set
```

## Usage example

```js
const FrequencySet = require("frequency-set");

const MySet = new FrequencySet(["foo", "bar"]);
MySet.add("foo");
MySet.add("foo");
MySet.add("bar");

console.log([...MySet.entries()]); // [["foo", 3], ["bar", 2]]

const clone = new FrequencySet(MySet);
console.log(clone);
```

## API
FrequencySet implements exactly the same interfaces as an ES6 [Set](https://developer.mozilla.org/fr/docs/Web/JavaScript/Reference/Objets_globaux/Set). Except for the **@@ Iteration Symbol** and the **entries()**. Instead of returning the unique value as key and value, FrequencySet return the unique value as key and the count as value.

```js
const mySet = new FrequencySet(["foo", "foo", "bar"]);

for (const [uniqueValue, count] of mySet) {
    console.log([uniqueValue, count]); // [foo, 2] and [bar, 1]
}
```

Also the add method has been extended with a additional `count` argument witch take a number.
```js
const mySet = new FrequencySet().add("foo", 10);

console.log(mySet.toJSON()); // ["foo", 10]
```

### toJSON()
FrequencySet implement a custom toJSON() method which will allow an automatic transformation into JSON.

```js
const mySet = new FrequencySet(["foo", "foo", "bar"]);

console.log(mySet.toJSON()); // [foo, 2] and [bar, 1];
```

The toJSON method does not take into account **functions** and **objects**.

## Contributors ✨

<!-- ALL-CONTRIBUTORS-BADGE:START - Do not remove or modify this section -->
[![All Contributors](https://img.shields.io/badge/all_contributors-1-orange.svg?style=flat-square)](#contributors-)
<!-- ALL-CONTRIBUTORS-BADGE:END -->

Thanks goes to these wonderful people ([emoji key](https://allcontributors.org/docs/en/emoji-key)):

<!-- ALL-CONTRIBUTORS-LIST:START - Do not remove or modify this section -->
<!-- prettier-ignore-start -->
<!-- markdownlint-disable -->
<table>
  <tr>
    <td align="center"><a href="https://www.linkedin.com/in/thomas-gentilhomme/"><img src="https://avatars.githubusercontent.com/u/4438263?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Gentilhomme</b></sub></a><br /><a href="https://github.com/fraxken/FrequencySet/commits?author=fraxken" title="Code">💻</a> <a href="https://github.com/fraxken/FrequencySet/issues?q=author%3Afraxken" title="Bug reports">🐛</a> <a href="https://github.com/fraxken/FrequencySet/pulls?q=is%3Apr+reviewed-by%3Afraxken" title="Reviewed Pull Requests">👀</a> <a href="https://github.com/fraxken/FrequencySet/commits?author=fraxken" title="Documentation">📖</a> <a href="#security-fraxken" title="Security">🛡️</a></td>
  </tr>
</table>

<!-- markdownlint-restore -->
<!-- prettier-ignore-end -->

<!-- ALL-CONTRIBUTORS-LIST:END -->

## License
MIT

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