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mapValues

Map values from one object to a new object having the same keys.

Installation

npm install @stdlib/utils-map-values

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 mapValues = require( '@stdlib/utils-map-values' );

mapValues( obj, transform )

Maps values from one object to a new object having the same keys.

function transform( value, key ) {
    return key + value;
}

var obj1 = {
    'a': 1,
    'b': 2
};

var obj2 = mapValues( obj1, transform );
// returns { 'a': 'a1', 'b': 'b2' }

The transform function is provided three arguments:

• value: object value corresponding to key.
• key: object key.
• obj: the input object.

Notes

• Key iteration order is not guaranteed, as object key enumeration is not specified according to the ECMAScript specification. In practice, however, most engines use insertion order to sort an object's keys, thus allowing for deterministic return values.
• The function only maps values assigned to own properties. Hence, the function does not map values for inherited properties.
• The function shallow copies key values.

Examples

var mapValues = require( '@stdlib/utils-map-values' );

function transform( value, key ) {
    return key + ':' + value;
}

var obj1 = {
    'a': 'beep',
    'b': 'boop',
    'c': 'foo',
    'd': 'bar'
};

var obj2 = mapValues( obj1, transform );

console.dir( obj2 );
// => { 'a': 'a:beep', 'b': 'b:boop', 'c': 'c:foo', 'd': 'd:bar' }

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See Also

• @stdlib/utils-map-keys: map keys from one object to a new object having the same values.
• @stdlib/utils-omit-by: return a partial object copy excluding properties for which a predicate (function) returns a truthy value.
• @stdlib/utils-pick-by: return a partial object copy containing properties for which a predicate (function) returns a truthy value.

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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.