# inheritedNonEnumerablePropertyNames
> Return an array of an object's inherited non-enumerable property names.
## Usage
```javascript
var inheritedNonEnumerablePropertyNames = require( '@stdlib/utils/inherited-nonenumerable-property-names' );
```
#### inheritedNonEnumerablePropertyNames( obj\[, level] )
Returns an `array` of an object's inherited non-enumerable property names.
```javascript
var defineProperty = require( '@stdlib/utils/define-property' );
function Foo() {
this.a = 'b';
return this;
}
defineProperty( Foo.prototype, 'beep', {
'configurable': false,
'enumerable': false,
'writable': false,
'value': 'boop'
});
var f = new Foo();
var keys = inheritedNonEnumerablePropertyNames( f );
// e.g., returns [ 'beep', ... ]
```
By default, the function walks an object's entire prototype chain. To limit the inheritance level, provide a `level` argument.
```javascript
var defineProperty = require( '@stdlib/utils/define-property' );
var inherit = require( '@stdlib/utils/inherit' );
function Bar() {
return this;
}
defineProperty( Bar.prototype, 'boop', {
'configurable': false,
'enumerable': false,
'writable': false,
'value': 'beep'
});
function Foo() {
Bar.call( this );
this.a = 'b';
return this;
}
inherit( Foo, Bar );
defineProperty( Foo.prototype, 'beep', {
'configurable': false,
'enumerable': false,
'writable': false,
'value': 'boop'
});
var f = new Foo();
var keys = inheritedNonEnumerablePropertyNames( f, 1 );
// e.g., returns [ 'beep', ... ]
```
## 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 inheritedNonEnumerablePropertyNames = require( '@stdlib/utils/inherited-nonenumerable-property-names' );
function Foo() {
this.beep = 'boop';
this.a = {
'b': 'c'
};
defineProperty( this, 'baz', {
'configurable': false,
'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 = inheritedNonEnumerablePropertyNames( obj );
console.log( keys );
// e.g., => [ 'bip', ... ]
```
[ecma-262-for-in]: http://www.ecma-international.org/ecma-262/5.1/#sec-12.6.4