# nonEnumerablePropertyNames
> Return an array of an object's own non-enumerable property names.
## Usage
```javascript
var nonEnumerablePropertyNames = require( '@stdlib/utils/nonenumerable-property-names' );
```
#### nonEnumerablePropertyNames( obj )
Returns an `array` of an object's own non-enumerable property names.
```javascript
var defineProperty = require( '@stdlib/utils/define-property' );
var obj = {
'a': 'b'
};
defineProperty( obj, 'c', {
'configurable': false,
'enumerable': false,
'writable': true,
'value': 'd'
});
var keys = nonEnumerablePropertyNames( obj );
// returns [ 'c' ]
```
## Notes
- Name order is not guaranteed, as `object` key enumeration is not specified according to the [ECMAScript specification][ecma-262-for-in]. In practice, however, most engines use insertion order to sort an `object`'s keys, thus allowing for deterministic extraction.
## Examples
```javascript
var defineProperty = require( '@stdlib/utils/define-property' );
var nonEnumerablePropertyNames = require( '@stdlib/utils/nonenumerable-property-names' );
function Foo() {
this.beep = 'boop';
this.a = {
'b': 'c'
};
defineProperty( this, 'baz', {
'configurable': true,
'enumerable': false,
'writable': true,
'value': 'qux'
});
return this;
}
Foo.prototype.foo = [ 'bar' ];
defineProperty( Foo.prototype, 'bip', {
'configurable': false,
'enumerable': false,
'writable': false,
'value': 'bop'
});
var obj = new Foo();
var keys = nonEnumerablePropertyNames( obj );
console.log( keys );
// => [ 'baz' ]
```
[ecma-262-for-in]: http://www.ecma-international.org/ecma-262/5.1/#sec-12.6.4