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

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[![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
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[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