@stdlib/utils-for-in

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


Keywords
stdlib, stdutils, stdutil, utilities, utility, utils, util, for, in, forin, object.keys, keys, properties, props, enumerable, inherited, inheritance, prototype, iterate, object, obj, javascript, node, node-js, nodejs
License
Apache-2.0
Install
npm install @stdlib/utils-for-in@0.0.7

Documentation

forIn

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

Installation

npm install @stdlib/utils-for-in

Usage

var forIn = require( '@stdlib/utils-for-in' );

forIn( obj, fcn[, thisArg ] )

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

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

function Foo() {
    this.a = 1;
    this.b = 2;
    return this;
}

Foo.prototype.c = 3;
Foo.prototype.d = 4;

var obj = new Foo();

forIn( 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
};

forIn( 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
};

forIn( obj, sum, context );

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

Notes

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

Examples

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

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

function Foo() {
    return this;
}

Foo.prototype.beep = 3.14;

var obj;
var key;
var i;

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

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

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.

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License

See LICENSE.

Copyright

Copyright © 2016-2021. The Stdlib Authors.