npm package: @stdlib/utils-nonindex-keys
Description: Return an array of an object's own enumerable property names which are not integer indices.
Author: The Stdlib Authors
Latest version: 0.2.3

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<details>
  <summary>
    About stdlib...
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# Non-Index Keys

[![NPM version][npm-image]][npm-url] [![Build Status][test-image]][test-url] [![Coverage Status][coverage-image]][coverage-url] <!-- [![dependencies][dependencies-image]][dependencies-url] -->

> Return an array of an object's own enumerable property names which are not integer indices.

<section class="installation">

## Installation

```bash
npm install @stdlib/utils-nonindex-keys
```

</section>

<section class="usage">

## Usage

```javascript
var nonIndexKeys = require( '@stdlib/utils-nonindex-keys' );
```

#### nonIndexKeys( obj )

Returns an `array` of an object's own enumerable property names which are not integer indices.

```javascript
var arr = [ 1, 2, 3 ];
arr.a = 'foo';
arr.b = 'bar';

var keys = nonIndexKeys( arr );
// e.g., returns [ 'a', 'b' ]
```

</section>

<!-- /.usage -->

<section class="notes">

## 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.
-   In contrast to the built-in `Object.keys()`, if provided `null` or `undefined`, the function returns an empty `array`, rather than throwing an error.

</section>

<!-- /.notes -->

<section class="examples">

## Examples

<!-- eslint no-undef: "error" -->

```javascript
var nonIndexKeys = require( '@stdlib/utils-nonindex-keys' );

function Foo() {
    this[ 0 ] = 3.14;
    this.beep = 'boop';
    this.a = {
        'b': 'c'
    };
    return this;
}

Foo.prototype.foo = [ 'bar' ];

var obj = new Foo();
var keys = nonIndexKeys( obj );

console.log( keys );
// e.g., => [ 'beep', 'a' ]
```

</section>

<!-- /.examples -->

<!-- Section for related `stdlib` packages. Do not manually edit this section, as it is automatically populated. -->

<section class="related">

* * *

## See Also

-   <span class="package-name">[`@stdlib/utils-entries`][@stdlib/utils/entries]</span><span class="delimiter">: </span><span class="description">return an array of an object's own enumerable property key-value pairs.</span>
-   <span class="package-name">[`@stdlib/utils-keys`][@stdlib/utils/keys]</span><span class="delimiter">: </span><span class="description">return an array of an object's own enumerable property names.</span>
-   <span class="package-name">[`@stdlib/utils-values`][@stdlib/utils/values]</span><span class="delimiter">: </span><span class="description">return an array of an object's own enumerable property values.</span>

</section>

<!-- /.related -->

<!-- Section for all links. Make sure to keep an empty line after the `section` element and another before the `/section` close. -->


<section class="main-repo" >

* * *

## Notice

This package is part of [stdlib][stdlib], a standard library for JavaScript and Node.js, with an emphasis on numerical and scientific computing. The library provides a collection of robust, high performance libraries for mathematics, statistics, streams, utilities, and more.

For more information on the project, filing bug reports and feature requests, and guidance on how to develop [stdlib][stdlib], see the main project [repository][stdlib].

#### Community

[![Chat][chat-image]][chat-url]

---

## License

See [LICENSE][stdlib-license].


## Copyright

Copyright &copy; 2016-2026. The Stdlib [Authors][stdlib-authors].

</section>

<!-- /.stdlib -->

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[npm-image]: http://img.shields.io/npm/v/@stdlib/utils-nonindex-keys.svg
[npm-url]: https://npmjs.org/package/@stdlib/utils-nonindex-keys

[test-image]: https://github.com/stdlib-js/utils-nonindex-keys/actions/workflows/test.yml/badge.svg?branch=v0.2.3
[test-url]: https://github.com/stdlib-js/utils-nonindex-keys/actions/workflows/test.yml?query=branch:v0.2.3

[coverage-image]: https://img.shields.io/codecov/c/github/stdlib-js/utils-nonindex-keys/main.svg
[coverage-url]: https://codecov.io/github/stdlib-js/utils-nonindex-keys?branch=main

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[stdlib]: https://github.com/stdlib-js/stdlib

[stdlib-authors]: https://github.com/stdlib-js/stdlib/graphs/contributors

[umd]: https://github.com/umdjs/umd
[es-module]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Guide/Modules

[deno-url]: https://github.com/stdlib-js/utils-nonindex-keys/tree/deno
[deno-readme]: https://github.com/stdlib-js/utils-nonindex-keys/blob/deno/README.md
[umd-url]: https://github.com/stdlib-js/utils-nonindex-keys/tree/umd
[umd-readme]: https://github.com/stdlib-js/utils-nonindex-keys/blob/umd/README.md
[esm-url]: https://github.com/stdlib-js/utils-nonindex-keys/tree/esm
[esm-readme]: https://github.com/stdlib-js/utils-nonindex-keys/blob/esm/README.md
[branches-url]: https://github.com/stdlib-js/utils-nonindex-keys/blob/main/branches.md

[stdlib-license]: https://raw.githubusercontent.com/stdlib-js/utils-nonindex-keys/main/LICENSE

[ecma-262-for-in]: https://262.ecma-international.org/5.1/#sec-12.6.4

<!-- <related-links> -->

[@stdlib/utils/entries]: https://www.npmjs.com/package/@stdlib/utils-entries

[@stdlib/utils/keys]: https://www.npmjs.com/package/@stdlib/utils-keys

[@stdlib/utils/values]: https://www.npmjs.com/package/@stdlib/utils-values

<!-- </related-links> -->

</section>

<!-- /.links -->