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


npm install @stdlib/utils-for-own


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


  • 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.


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 );

See Also


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.






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  • stdlib-bot
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