@stdlib/utils-map-keys/README.md

Map keys from one object to a new object having the same values.

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# mapKeys

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> Map keys from one object to a new object having the same values.

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<section class="installation">

## Installation

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

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<section class="usage">

## Usage

```javascript
var mapKeys = require( '@stdlib/utils-map-keys' );
```

#### mapKeys( obj, transform )

Map keys from one `object` to a new `object` having the same values.

```javascript
function transform( key, value ) {
    return key + value;
}

var obj1 = {
    'a': 1,
    'b': 2
};

var obj2 = mapKeys( obj1, transform );
// returns { 'a1': 1, 'b2': 2 }
```

The `transform` function is provided three arguments:

-   `key`: object key
-   `value`: object value corresponding to `key`
-   `obj`: the input object

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<!-- Package usage notes. Make sure to keep an empty line after the `section` element and another before the `/section` close. -->

<section class="notes">

## Notes

-   Key iteration 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 return values.
-   The function only maps **own** properties. Hence, the function does **not** map inherited properties.
-   The function **shallow** copies key values.
-   The value returned by a `transform` function should be a value which can be serialized as an `object` key.

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## Examples

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

```javascript
var mapKeys = require( '@stdlib/utils-map-keys' );

function transform( key, value ) {
    return key + ':' + value;
}

var obj1 = {
    'a': 'beep',
    'b': 'boop',
    'c': 'foo',
    'd': 'bar'
};

var obj2 = mapKeys( obj1, transform );

console.dir( obj2 );
// => { 'a:beep': 'beep', 'b:boop': 'boop', 'c:foo': 'foo', 'd:bar': 'bar' }
```

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* * *

## See Also

-   <span class="package-name">[`@stdlib/utils-map-values`][@stdlib/utils/map-values]</span><span class="delimiter">: </span><span class="description">map values from one object to a new object having the same keys.</span>

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<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

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---

## License

See [LICENSE][stdlib-license].


## Copyright

Copyright &copy; 2016-2024. The Stdlib [Authors][stdlib-authors].

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

[test-image]: https://github.com/stdlib-js/utils-map-keys/actions/workflows/test.yml/badge.svg?branch=v0.2.2
[test-url]: https://github.com/stdlib-js/utils-map-keys/actions/workflows/test.yml?query=branch:v0.2.2

[coverage-image]: https://img.shields.io/codecov/c/github/stdlib-js/utils-map-keys/main.svg
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[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-map-keys/tree/deno
[deno-readme]: https://github.com/stdlib-js/utils-map-keys/blob/deno/README.md
[umd-url]: https://github.com/stdlib-js/utils-map-keys/tree/umd
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[esm-url]: https://github.com/stdlib-js/utils-map-keys/tree/esm
[esm-readme]: https://github.com/stdlib-js/utils-map-keys/blob/esm/README.md
[branches-url]: https://github.com/stdlib-js/utils-map-keys/blob/main/branches.md

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

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

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

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</section>

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