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forOwn

Invoke a function for each own enumerable property of an object.

Installation

npm install @stdlib/utils-for-own

Alternatively,

• To load the package in a website via a script tag without installation and bundlers, use the ES Module available on the esm branch (see README).
• If you are using Deno, visit the deno branch (see README for usage intructions).
• For use in Observable, or in browser/node environments, use the Universal Module Definition (UMD) build available on the umd branch (see README).

The branches.md 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

var forOwn = require( '@stdlib/utils-for-own' );

forOwn( obj, fcn[, thisArg ] )

Invokes a function for each own enumerable property of an object.

function log( value, key ) {
    console.log( '%s: %d', key, value );
}

var obj = {
    'a': 1,
    'b': 2,
    'c': 3,
    'd': 4
};

forOwn( obj, log );
/* e.g., =>
    a: 1
    b: 2
    c: 3
    d: 4
*/

The invoked function is provided three arguments:

• value: object property value.
• key: object property.
• obj: the input object.

To terminate iteration before visiting all properties, the provided function must explicitly return false.

function log( value, key ) {
    console.log( '%s: %d', key, value );
    return false;
}

var obj = {
    'a': 1,
    'b': 2,
    'c': 3,
    'd': 4
};

forOwn( obj, log );
// e.g., => a: 1

To set the function execution context, provide a thisArg.

function sum( value ) {
    this.sum += value;
    this.count += 1;
}

var obj = {
    'a': 1,
    'b': 2,
    'c': 3,
    'd': 4
};

var context = {
    'sum': 0,
    'count': 0
};

forOwn( obj, sum, context );

var mean = context.sum / context.count;
// returns 2.5

Notes

• The function returns the input object.
• 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.
• Property iteration order is not guaranteed.

Examples

var fromCodePoint = require( '@stdlib/string-from-code-point' );
var forOwn = require( '@stdlib/utils-for-own' );

function update( value, key, obj ) {
    console.log( '%s: %d', key, value );
    obj[ key ] *= value;
}

var obj;
var key;
var i;

obj = {};
for ( i = 0; i < 26; i++ ) {
    key = fromCodePoint( 97 + i );
    obj[ key ] = i;
}

forOwn( obj, update );
console.log( obj );

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See Also

• @stdlib/utils-for-each: invoke a function for each element in a collection.
• @stdlib/utils-for-in: invoke a function for each own and inherited enumerable property of an object.

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Notice

This package is part of 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, see the main project repository.

Community

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License

See LICENSE.

Copyright

Copyright © 2016-2024. The Stdlib Authors.