# internal-slot

> ES spec-like internal slots

Latest version **1.1.0** (published 2024-12-13) · MIT license · 0 weekly downloads

## Install

```sh
npm install internal-slot
pnpm add internal-slot
yarn add internal-slot
bun add internal-slot
```

## Health

**Score 35/100 (D)** — status: maintenance-mode.

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

Warnings: low downloads; no esm support.

Negative: stale; low maintenance score.

## Facts

| | |
|---|---|
| Version | 1.1.0 |
| Published | 2024-12-13 |
| First published | 2019-10-21 |
| Weekly downloads | 0 |
| License | MIT |
| TypeScript types | bundled |
| Module format | CommonJS |
| Node | >= 0.4 |
| Dependencies | 3 |
| Unpacked size | 22.5 KB |
| Known vulnerabilities | 0 |
| Install scripts | no |
| GitHub stars | 9 |
| Author | Jordan Harband |
| Maintainers | ljharb |
| Keywords | internal, slot, internal slot, ecmascript, es, spec, private, data, private data, weakmap |

## Links

- npm: https://www.npmjs.com/package/internal-slot
- Repository: https://github.com/ljharb/internal-slot
- Homepage: https://github.com/ljharb/internal-slot#readme
- Issues: https://github.com/ljharb/internal-slot/issues
- npm.io page: https://npm.io/package/internal-slot

## Dependencies (3)

- [hasown](https://npm.io/package/hasown.md) ^2.0.2
- [es-errors](https://npm.io/package/es-errors.md) ^1.3.0
- [side-channel](https://npm.io/package/side-channel.md) ^1.1.0

## Alternatives

- [duck](https://npm.io/package/duck.md) — 4.2M weekly downloads
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- [@ethereum-waffle/mock-contract](https://npm.io/package/@ethereum-waffle/mock-contract.md) — 40.0K weekly downloads

## Recent versions

- 1.1.0 (latest) — 2024-12-13
- 1.0.7 — 2024-02-06
- 1.0.6 — 2023-10-21
- 1.0.5 — 2023-02-09
- 1.0.4 — 2022-12-13
- 1.0.3 — 2021-01-26
- 1.0.2 — 2019-12-20
- 1.0.1 — 2019-12-02
- 1.0.0 — 2019-10-21

## README

# internal-slot <sup>[![Version Badge][npm-version-svg]][package-url]</sup>

[![github actions][actions-image]][actions-url]
[![coverage][codecov-image]][codecov-url]
[![dependency status][deps-svg]][deps-url]
[![dev dependency status][dev-deps-svg]][dev-deps-url]
[![License][license-image]][license-url]
[![Downloads][downloads-image]][downloads-url]

[![npm badge][npm-badge-png]][package-url]

Truly private storage, akin to the JS spec’s concept of internal slots.

Uses a WeakMap when available; a Map when not; and a regular object in even older engines. Performance and garbage collection behavior will reflect the environment’s capabilities accordingly.

## Example

```js
var SLOT = require('internal-slot');
var assert = require('assert');

var o = {};

assert.throws(function () { SLOT.assert(o, 'foo'); });

assert.equal(SLOT.has(o, 'foo'), false);
assert.equal(SLOT.get(o, 'foo'), undefined);

SLOT.set(o, 'foo', 42);

assert.equal(SLOT.has(o, 'foo'), true);
assert.equal(SLOT.get(o, 'foo'), 42);

assert.doesNotThrow(function () { SLOT.assert(o, 'foo'); });
```

## Tests
Simply clone the repo, `npm install`, and run `npm test`

## Security

Please email [@ljharb](https://github.com/ljharb) or see https://tidelift.com/security if you have a potential security vulnerability to report.

[package-url]: https://npmjs.org/package/internal-slot
[npm-version-svg]: https://versionbadg.es/ljharb/internal-slot.svg
[deps-svg]: https://david-dm.org/ljharb/internal-slot.svg
[deps-url]: https://david-dm.org/ljharb/internal-slot
[dev-deps-svg]: https://david-dm.org/ljharb/internal-slot/dev-status.svg
[dev-deps-url]: https://david-dm.org/ljharb/internal-slot#info=devDependencies
[npm-badge-png]: https://nodei.co/npm/internal-slot.png?downloads=true&stars=true
[license-image]: https://img.shields.io/npm/l/internal-slot.svg
[license-url]: LICENSE
[downloads-image]: https://img.shields.io/npm/dm/internal-slot.svg
[downloads-url]: https://npm-stat.com/charts.html?package=internal-slot
[codecov-image]: https://codecov.io/gh/ljharb/internal-slot/branch/main/graphs/badge.svg
[codecov-url]: https://app.codecov.io/gh/ljharb/internal-slot/
[actions-image]: https://img.shields.io/endpoint?url=https://github-actions-badge-u3jn4tfpocch.runkit.sh/ljharb/internal-slot
[actions-url]: https://github.com/ljharb/internal-slot/actions

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