is-data-descriptor

What is is-data-descriptor?

The is-data-descriptor npm package is used to determine if an object is a valid data descriptor. Data descriptors are object keys that have attributes like value, writable, enumerable, and configurable. This package checks if a given object conforms to the specification of a data descriptor.

What are is-data-descriptor's main functionalities?

Check if an object is a data descriptor

This feature allows you to verify if a given object is a valid data descriptor by checking its properties and their respective values.

const isDataDescriptor = require('is-data-descriptor');

const descriptor = {value: 'value', writable: true, enumerable: true, configurable: true};
const result = isDataDescriptor(descriptor); // result is true

Other packages similar to is-data-descriptor

is-descriptor

This package is more general than is-data-descriptor. It checks if an object is any kind of descriptor, including data and accessor descriptors. It is a superset of is-data-descriptor functionality.

is-accessor-descriptor

Similar to is-data-descriptor, but specifically checks if an object is a valid accessor descriptor, which includes properties like get, set, enumerable, and configurable.

kind-of

While not limited to descriptors, this utility module can check the type of any JavaScript value, including whether it is a descriptor. It is more versatile but less specialized than is-data-descriptor.

README

is-data-descriptor

Returns true if a value has the characteristics of a valid JavaScript data descriptor.

Install

Install with npm:

$ npm install --save is-data-descriptor

Usage

var isDataDesc = require('is-data-descriptor');
var assert = require('assert');

Examples

true when the descriptor has valid properties with valid values.

// `value` can be anything
assert.equal(isDataDesc({ value: 'foo' }), true);
assert.equal(isDataDesc({ value: function () {} }), true);
assert.equal(isDataDesc({ value: true }), true);

false when not an object

assert.equal(isDataDesc('a'), false);
assert.equal(isDataDesc(null), false);

false when the object has invalid properties

assert.equal(isDataDesc({ value: 'foo', enumerable: 'baz' }), false);
assert.equal(isDataDesc({ value: 'foo', configurable: 'baz' }), false);
assert.equal(isDataDesc({ value: 'foo', get() {} }), false);
assert.equal(isDataDesc({ get() {}, value: 'foo' }), false);

false when a value is not the correct type

assert.equal(isDataDesc({ value: 'foo', enumerable: 'foo' }), false);
assert.equal(isDataDesc({ value: 'foo', configurable: 'foo' }), false);
assert.equal(isDataDesc({ value: 'foo', writable: 'foo' }), false);

Valid properties

The only valid data descriptor properties are the following:

• configurable (required)
• enumerable (required)
• value (optional)
• writable (optional)

To be a valid data descriptor, either value or writable must be defined.

Invalid properties

A descriptor may have additional invalid properties (an error will not be thrown).

var foo = {};

Object.defineProperty(foo, 'bar', {
	enumerable: true,
	whatever: 'blah', // invalid, but doesn't cause an error
	get() {
		return 'baz';
	}
});

assert.equal(foo.bar, 'baz');

Related projects

You might also be interested in these projects:

• is-accessor-descriptor: Returns true if a value has the characteristics of a valid JavaScript accessor descriptor.
• is-descriptor: Returns true if a value has the characteristics of a valid JavaScript descriptor. Works for… more

Changelog

v1.0.1 - 2023-10-26

Commits

• [eslint] actually use eslint 65fed07
• [readme] clean up readme, remove verb 10ad663
• [meta] clean up package.json 7f76a01
• [meta] update .gitignore a2ca593
• [Tests] switch to tape 70540e5
• [Tests] migrate from travis to github actions eee138d
• [Fix] properly return false for an accessor descriptor 2c213cd
• [Performance] move data object to module level 37688a1
• [Fix] allow any non-primitive; arrays and functions are objects too 197c77a
• Only apps should have lockfiles 20aa6e5
• [Robustness] switch to hasown aa48e2f
• [Fix] properly guard for-in loop 014971e
• [Robustness] use a null object just in case ab05aad