https://github.com/inspect-js/is-descriptor
Returns true if a value has the characteristics of a valid JavaScript descriptor. Works for data descriptors and accessor descriptors.
https://github.com/inspect-js/is-descriptor
accessor accessor-descriptor data-descriptor descriptor javascript node nodejs
Last synced: 5 months ago
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Returns true if a value has the characteristics of a valid JavaScript descriptor. Works for data descriptors and accessor descriptors.
- Host: GitHub
- URL: https://github.com/inspect-js/is-descriptor
- Owner: inspect-js
- License: mit
- Created: 2015-08-31T06:09:39.000Z (almost 11 years ago)
- Default Branch: main
- Last Pushed: 2023-10-28T05:21:40.000Z (over 2 years ago)
- Last Synced: 2025-03-10T04:35:23.719Z (about 1 year ago)
- Topics: accessor, accessor-descriptor, data-descriptor, descriptor, javascript, node, nodejs
- Language: JavaScript
- Homepage:
- Size: 97.7 KB
- Stars: 12
- Watchers: 4
- Forks: 4
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
- Changelog: CHANGELOG.md
- Funding: .github/FUNDING.yml
- License: LICENSE
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README
# is-descriptor [![Version Badge][npm-version-svg]][package-url]
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[![License][license-image]][license-url]
[![Downloads][downloads-image]][downloads-url]
[![npm badge][npm-badge-png]][package-url]
> Returns true if a value has the characteristics of a valid JavaScript descriptor. Works for fully completed data descriptors and accessor descriptors.
## Usage
```js
const isDescriptor = require('is-descriptor');
const assert = require('assert');
const defaults = { configurable: false, enumerable: false };
const dataDefaults = { ...defaults, writable: false};
assert.ok(isDescriptor({ ...dataDefaults, value: 'foo' }));
assert.ok(isDescriptor({ ...defaults, get() {}, set() {} }));
assert.ok(!isDescriptor({ ...defaults, get: 'foo', set() {} }));
```
You may also check for a descriptor by passing an object as the first argument and property name (`string`) as the second argument.
```js
const obj = { foo: 'abc' };
Object.defineProperty(obj, 'bar', { value: 'xyz' });
Reflect.defineProperty(obj, 'baz', { value: 'xyz' });
assert.equal(isDescriptor(obj, 'foo'), true);
assert.equal(isDescriptor(obj, 'bar'), true);
assert.equal(isDescriptor(obj, 'baz'), true);
```
## Examples
### value type
Returns `false` when not an object
```js
assert.equal(isDescriptor('a'), false);
assert.equal(isDescriptor(null), false);
assert.equal(isDescriptor([]), false);
```
### data descriptor
Returns `true` when the object has valid properties with valid values.
```js
assert.equal(isDescriptor({ ...dataDefaults, value: 'foo' }), true);
assert.equal(isDescriptor({ ...dataDefaults, value() {} }), true);
```
Returns `false` when the object has invalid properties
```js
assert.equal(isDescriptor({ ...dataDefaults, value: 'foo', bar: 'baz' }), false);
assert.equal(isDescriptor({ ...dataDefaults, value: 'foo', bar: 'baz' }), false);
assert.equal(isDescriptor({ ...dataDefaults, value: 'foo', enumerable: 'baz' }), false);
assert.equal(isDescriptor({ ...dataDefaults, value: 'foo', configurable: 'baz' }), false);
assert.equal(isDescriptor({ ...dataDefaults, value: 'foo', get() {} }), false);
assert.equal(isDescriptor({ ...dataDefaults, get() {}, value() {} }), false);
```
`false` when a value is not the correct type
```js
assert.equal(isDescriptor({ ...dataDefaults, value: 'foo', enumerable: 'foo' }), false);
assert.equal(isDescriptor({ ...dataDefaults, value: 'foo', configurable: 'foo' }), false);
assert.equal(isDescriptor({ ...dataDefaults, value: 'foo', writable: 'foo' }), false);
```
### accessor descriptor
`true` when the object has valid properties with valid values.
```js
assert.equal(isDescriptor({ ...defaults, get() {}, set() {} }), true);
assert.equal(isDescriptor({ ...defaults, get() {} }), true);
assert.equal(isDescriptor({ ...defaults, set() {} }), true);
```
`false` when the object has invalid properties
```js
assert.equal(isDescriptor({ ...defaults, get() {}, set() {}, bar: 'baz' }), false);
assert.equal(isDescriptor({ ...defaults, get() {}, set() {}, enumerable: 'baz' }), false);
assert.equal(isDescriptor({ ...defaults, get() {}, writable: true }), false);
assert.equal(isDescriptor({ ...defaults, get() {}, value: true }), false);
```
Returns `false` when an accessor is not a function
```js
assert.equal(isDescriptor({ ...defaults, get() {}, set: 'baz' }), false);
assert.equal(isDescriptor({ ...defaults, get: 'foo', set() {} }), false);
assert.equal(isDescriptor({ ...defaults, get: 'foo', bar: 'baz' }), false);
assert.equal(isDescriptor({ ...defaults, get: 'foo', set: 'baz' }), false);
```
Returns `false` when a value is not the correct type
```js
assert.equal(isDescriptor({ ...defaults, get() {}, set() {}, enumerable: 'foo' }), false);
assert.equal(isDescriptor({ ...defaults, set() {}, configurable: 'foo' }), false);
assert.equal(isDescriptor({ ...defaults, get() {}, configurable: 'foo' }), false);
```
### Related projects
You might also be interested in these projects:
* [is-accessor-descriptor](https://www.npmjs.com/package/is-accessor-descriptor): Returns true if a value has the characteristics of a valid JavaScript accessor descriptor.
* [is-data-descriptor](https://www.npmjs.com/package/is-data-descriptor): Returns true if a value has the characteristics of a valid JavaScript data descriptor.
* [is-object](https://www.npmjs.com/package/is-object): Returns true if the value is an object and not an array or null.
## Tests
Simply clone the repo, `npm install`, and run `npm test`
[package-url]: https://npmjs.org/package/is-descriptor
[npm-version-svg]: https://versionbadg.es/inspect-js/is-descriptor.svg
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[deps-url]: https://david-dm.org/inspect-js/is-descriptor
[dev-deps-svg]: https://david-dm.org/inspect-js/is-descriptor/dev-status.svg
[dev-deps-url]: https://david-dm.org/inspect-js/is-descriptor#info=devDependencies
[npm-badge-png]: https://nodei.co/npm/is-descriptor.png?downloads=true&stars=true
[license-image]: https://img.shields.io/npm/l/is-descriptor.svg
[license-url]: LICENSE
[downloads-image]: https://img.shields.io/npm/dm/is-descriptor.svg
[downloads-url]: https://npm-stat.com/charts.html?package=is-descriptor
[codecov-image]: https://codecov.io/gh/inspect-js/is-descriptor/branch/main/graphs/badge.svg
[codecov-url]: https://app.codecov.io/gh/inspect-js/is-descriptor/
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[actions-url]: https://github.com/inspect-js/is-descriptor/actions