uniIM/node_modules/is-data-descriptor

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