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forIn

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

Installation

npm install @stdlib/utils-for-in

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 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 );

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See Also

• @stdlib/utils-for-each: invoke a function for each element in a collection.
• @stdlib/utils-for-own: invoke a function for each own 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.