is-descriptor

is-descriptor

Returns true if a value has the characteristics of a valid JavaScript descriptor. Works for fully completed data descriptors and accessor descriptors.

Usage

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.

const obj = {}; obj.foo = null; Object.defineProperty(obj, 'bar', { value: 'xyz' }); Reflect.defineProperty(obj, 'baz', { value: 'xyz' }); assert.ok(isDescriptor(obj, 'foo')); assert.ok(isDescriptor(obj, 'bar')); assert.ok(isDescriptor(obj, 'baz'));

Examples

value type

Returns false when not an object

assert.ok(!isDescriptor('a')); assert.ok(!isDescriptor(null)); assert.ok(!isDescriptor([]));

data descriptor

Returns true when the object has valid properties with valid values.

assert.ok(isDescriptor({ ...dataDefaults, value: 'foo' })); assert.ok(isDescriptor({ ...dataDefaults, value() {} }));

Returns false when the object has invalid properties

assert.ok(!isDescriptor({ ...dataDefaults, value: 'foo', bar: 'baz' })); assert.ok(!isDescriptor({ ...dataDefaults, value: 'foo', bar: 'baz' })); assert.ok(!isDescriptor({ ...dataDefaults, value: 'foo', get() {} })); assert.ok(!isDescriptor({ ...dataDefaults, get() {}, value() {} }));

false when a value is not the correct type

assert.ok(!isDescriptor({ ...dataDefaults, value: 'foo', enumerable: 'foo'})); assert.ok(!isDescriptor({ ...dataDefaults, value: 'foo', configurable: 'foo'})); assert.ok(!isDescriptor({ ...dataDefaults, value: 'foo', writable: 'foo'}));

accessor descriptor

true when the object has valid properties with valid values.

assert.ok(isDescriptor({ ...defaults, get() {}, set() {} })); assert.ok(isDescriptor({ ...defaults, get() {} })); assert.ok(isDescriptor({ ...defaults, set() {} }));

false when the object has invalid properties

assert.ok(!isDescriptor({ ...defaults, get() {}, set() {}, bar: 'baz' })); assert.ok(!isDescriptor({ ...defaults, get() {}, writable: true })); assert.ok(!isDescriptor({ ...defaults, get() {}, value: true }));

Returns false when an accessor is not a function

assert.ok(!isDescriptor({ ...defaults, get() {}, set: 'baz' })); assert.ok(!isDescriptor({ ...defaults, get: 'foo', set() {} })); assert.ok(!isDescriptor({ ...defaults, get: 'foo', bar: 'baz' })); assert.ok(!isDescriptor({ ...defaults, get: 'foo', set: 'baz' }));

Returns false when a value is not the correct type

assert.ok(!isDescriptor({ ...defaults, get() {}, set() {}, enumerable: 'foo' })); assert.ok(!isDescriptor({ ...defaults, set() {}, configurable: 'foo' })); assert.ok(!isDescriptor({ ...defaults, get() {}, configurable: 'foo' }));

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