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


npm install @stdlib/utils-map-keys


var mapKeys = require( '@stdlib/utils-map-keys' );

mapKeys( obj, transform )

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

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

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

var obj2 = mapKeys( obj1, transform );
// returns { 'a1': 1, 'b2': 2 }

The transform function is provided three arguments:

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


  • 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 own properties. Hence, the function does not map inherited properties.
  • The function shallow copies key values.
  • The value returned by a transform function should be a value which can be serialized as an object key.


var mapKeys = require( '@stdlib/utils-map-keys' );

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

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

var obj2 = mapKeys( obj1, transform );

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

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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