https://github.com/stdlib-js/utils-group-own
Group an object's own property values according to an indicator function.
https://github.com/stdlib-js/utils-group-own
aggregate group group-by groupby javascript node node-js nodejs obj object own partition split stdlib util utilities utility utils
Last synced: 28 days ago
JSON representation
Group an object's own property values according to an indicator function.
- Host: GitHub
- URL: https://github.com/stdlib-js/utils-group-own
- Owner: stdlib-js
- License: apache-2.0
- Created: 2021-06-14T16:41:30.000Z (almost 4 years ago)
- Default Branch: main
- Last Pushed: 2025-03-31T00:49:17.000Z (about 2 months ago)
- Last Synced: 2025-04-23T16:28:06.220Z (28 days ago)
- Topics: aggregate, group, group-by, groupby, javascript, node, node-js, nodejs, obj, object, own, partition, split, stdlib, util, utilities, utility, utils
- Language: JavaScript
- Homepage: https://github.com/stdlib-js/stdlib
- Size: 1.13 MB
- Stars: 1
- Watchers: 3
- Forks: 0
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
- Changelog: CHANGELOG.md
- Contributing: CONTRIBUTING.md
- License: LICENSE
- Code of conduct: CODE_OF_CONDUCT.md
- Citation: CITATION.cff
- Security: SECURITY.md
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README
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# groupOwn
[![NPM version][npm-image]][npm-url] [![Build Status][test-image]][test-url] [![Coverage Status][coverage-image]][coverage-url]
> Group an object's **own** property values according to an indicator function.
## Installation
```bash
npm install @stdlib/utils-group-own
```
Alternatively,
- To load the package in a website via a `script` tag without installation and bundlers, use the [ES Module][es-module] available on the [`esm`][esm-url] branch (see [README][esm-readme]).
- If you are using Deno, visit the [`deno`][deno-url] branch (see [README][deno-readme] for usage intructions).
- For use in Observable, or in browser/node environments, use the [Universal Module Definition (UMD)][umd] build available on the [`umd`][umd-url] branch (see [README][umd-readme]).
The [branches.md][branches-url] file summarizes the available branches and displays a diagram illustrating their relationships.
To view installation and usage instructions specific to each branch build, be sure to explicitly navigate to the respective README files on each branch, as linked to above.
## Usage
```javascript
var groupOwn = require( '@stdlib/utils-group-own' );
```
#### groupOwn( obj, \[options,] indicator )
Groups an object's **own** property values according to an `indicator` function, which specifies which group a value in the input `object` belongs to.
```javascript
function indicator( v ) {
return v[ 0 ];
}
var obj = {
'a': 'beep',
'b': 'boop',
'c': 'foo',
'd': 'bar'
};
var out = groupOwn( obj, indicator );
// e.g., returns { 'b': [ 'beep', 'boop', 'bar' ], 'f': [ 'foo' ] }
```
An `indicator` function is provided two arguments:
- **value**: object value.
- **key**: object index.
```javascript
function indicator( v, k ) {
console.log( '%s: %s', k, v );
return v[ 0 ];
}
var obj = {
'a': 'beep',
'b': 'boop',
'c': 'foo',
'd': 'bar'
};
var out = groupOwn( obj, indicator );
// e.g., returns { 'b': [ 'beep', 'boop', 'bar' ], 'f': [ 'foo' ] }
```
The function accepts the following `options`:
- **returns**: specifies the output format. If the option equals `'values'`, the function outputs values. If the option equals `'keys'`, the function outputs keys. If the option equals `'*'`, the function outputs both keys and values. Default: `'values'`.
- **thisArg**: execution context.
By default, the function returns object values. To return object keys, set the `returns` option to `'keys'`.
```javascript
function indicator( v ) {
return v[ 0 ];
}
var obj = {
'a': 'beep',
'b': 'boop',
'c': 'foo',
'd': 'bar'
};
var opts = {
'returns': 'keys'
};
var out = groupOwn( obj, opts, indicator );
// e.g., returns { 'b': [ 'a', 'b', 'd' ], 'f': [ 'c' ] }
```
To return key-value pairs, set the `returns` option to `'*'`.
```javascript
function indicator( v ) {
return v[ 0 ];
}
var obj = {
'a': 'beep',
'b': 'boop',
'c': 'foo',
'd': 'bar'
};
var opts = {
'returns': '*'
};
var out = groupOwn( obj, opts, indicator );
// e.g., returns { 'b': [ [ 'a', 'beep' ], [ 'b', 'boop ], [ 'd', 'bar' ] ], 'f': [ [ 'c', 'foo' ] ] }
```
To set the `indicator` execution context, provide a `thisArg`.
```javascript
function indicator( v ) {
this.count += 1;
return v[ 0 ];
}
var context = {
'count': 0
};
var opts = {
'thisArg': context
};
var obj = {
'a': 'beep',
'b': 'boop',
'c': 'foo',
'd': 'bar'
};
var out = groupOwn( obj, opts, indicator );
// e.g., returns { 'b': [ 'beep', 'boop', 'bar' ], 'f': [ 'foo' ] }
console.log( context.count );
// => 4
```
## Notes
- 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 iteration.
- Because iteration order is **not** guaranteed, result order is **not** guaranteed.
- The function determines the list of own enumerable properties **before** invoking the provided function. Hence, any modifications made to the input `object` **after** calling this function (such as adding and removing properties) will **not** affect the list of visited properties.
- The value returned by an `indicator` function should be a value which can be serialized as an `object` key. As a counterexample,
```javascript
function indicator( v ) {
return {};
}
var obj = {
'a': 'beep',
'b': 'boop',
'c': 'foo',
'd': 'bar'
};
var out = groupOwn( obj, indicator );
// e.g., returns { '[object Object]': [ 'beep', 'boop', 'foo', 'bar' ] }
```
while each group identifier is unique, all object values resolve to the same group because each group identifier serializes to the same `string`.
## Examples
```javascript
var randu = require( '@stdlib/random-base-randu' );
var fromCodePoint = require( '@stdlib/string-from-code-point' );
var groupOwn = require( '@stdlib/utils-group-own' );
var key;
var obj;
var out;
var i;
// Generate a random object...
obj = {};
for ( i = 0; i < 100; i++ ) {
key = fromCodePoint( 97+i );
obj[ key ] = randu();
}
function indicator( v ) {
if ( v < 0.5 ) {
return 'low';
}
return 'high';
}
// Compute the groups:
out = groupOwn( obj, indicator );
console.log( out );
```
* * *
## See Also
- [`@stdlib/utils-bifurcate-own`][@stdlib/utils/bifurcate-own]: split an object's own property values into two groups according to a predicate function.
- [`@stdlib/utils-group`][@stdlib/utils/group]: group values as arrays associated with distinct keys.
- [`@stdlib/utils-group-by`][@stdlib/utils/group-by]: group values according to an indicator function.
* * *
## 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 © 2016-2025. The Stdlib [Authors][stdlib-authors].
[npm-image]: http://img.shields.io/npm/v/@stdlib/utils-group-own.svg
[npm-url]: https://npmjs.org/package/@stdlib/utils-group-own
[test-image]: https://github.com/stdlib-js/utils-group-own/actions/workflows/test.yml/badge.svg?branch=main
[test-url]: https://github.com/stdlib-js/utils-group-own/actions/workflows/test.yml?query=branch:main
[coverage-image]: https://img.shields.io/codecov/c/github/stdlib-js/utils-group-own/main.svg
[coverage-url]: https://codecov.io/github/stdlib-js/utils-group-own?branch=main
[chat-image]: https://img.shields.io/gitter/room/stdlib-js/stdlib.svg
[chat-url]: https://app.gitter.im/#/room/#stdlib-js_stdlib:gitter.im
[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-group-own/tree/deno
[deno-readme]: https://github.com/stdlib-js/utils-group-own/blob/deno/README.md
[umd-url]: https://github.com/stdlib-js/utils-group-own/tree/umd
[umd-readme]: https://github.com/stdlib-js/utils-group-own/blob/umd/README.md
[esm-url]: https://github.com/stdlib-js/utils-group-own/tree/esm
[esm-readme]: https://github.com/stdlib-js/utils-group-own/blob/esm/README.md
[branches-url]: https://github.com/stdlib-js/utils-group-own/blob/main/branches.md
[stdlib-license]: https://raw.githubusercontent.com/stdlib-js/utils-group-own/main/LICENSE
[ecma-262-for-in]: https://262.ecma-international.org/5.1/#sec-12.6.4
[@stdlib/utils/bifurcate-own]: https://github.com/stdlib-js/utils-bifurcate-own
[@stdlib/utils/group]: https://github.com/stdlib-js/utils-group
[@stdlib/utils/group-by]: https://github.com/stdlib-js/utils-group-by