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Get array of object's keys

How to get collection of keys in javascript dictionary?HashMap objects in javascriptForm array of property names found in a JavaScript ObjectHow to access all JSON array nameHow to access the item in an object of an array by index number?Javascript extract object names to an arrayParsing JSON keys into array of stringsBasic «reflection» in JSHow to convert an Object to an Array [] in JavaScriptAssign object variable name to a variable javascript or typescriptHow do you get a timestamp in JavaScript?How do I check if an array includes an object in JavaScript?Get the name of an object's typeHow to append something to an array?How do you check if a variable is an array in JavaScript?Checking if a key exists in a JavaScript object?Loop through an array in JavaScriptHow do I remove a particular element from an array in JavaScript?For-each over an array in JavaScript?JavaScript set object key by variable

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318

49

I would like to get the keys of a JavaScript object as an array, either in jQuery or pure JavaScript.

Is there a less verbose way than this?

var foo = 'alpha' : 'puffin', 'beta' : 'beagle' ;
var keys = [];
for (var key in foo) 
 keys.push(key);

javascript ecmascript-5

share|improve this question

edited Jan 12 '18 at 21:45

dreftymac

16.4k2191154

asked Jan 6 '12 at 19:12

RichardRichard

10.9k2391141

• 
  
  
  

  
  4
  

  
  
  
  
  
  

  
  
  Besides from adding if(foo.hasOwnProperty(key)), that's what I'd do. Or, use $.map.
  
  – Rocket Hazmat
  Jan 6 '12 at 19:17
  

  
  
  
  


• 
  
  
  

  
  9
  

  
  
  
  
  
  

  
  
  Oh for a Pythonic one-liner, though...
  
  – Richard
  Jan 6 '12 at 19:17
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  an old question so not worth a full answer, but for those who want to fiddle... jsfiddle.net/LR5D9/3 this solution deals with the issue of prototype declarations messing up for var in x loops
  
  – unsynchronized
  Jul 13 '14 at 1:56
  
  

  
  
  
  

add a comment | 

318

49

I would like to get the keys of a JavaScript object as an array, either in jQuery or pure JavaScript.

Is there a less verbose way than this?

var foo = 'alpha' : 'puffin', 'beta' : 'beagle' ;
var keys = [];
for (var key in foo) 
 keys.push(key);

javascript ecmascript-5

share|improve this question

edited Jan 12 '18 at 21:45

dreftymac

16.4k2191154

asked Jan 6 '12 at 19:12

RichardRichard

10.9k2391141

• 
  
  
  

  
  4
  

  
  
  
  
  
  

  
  
  Besides from adding if(foo.hasOwnProperty(key)), that's what I'd do. Or, use $.map.
  
  – Rocket Hazmat
  Jan 6 '12 at 19:17
  

  
  
  
  


• 
  
  
  

  
  9
  

  
  
  
  
  
  

  
  
  Oh for a Pythonic one-liner, though...
  
  – Richard
  Jan 6 '12 at 19:17
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  an old question so not worth a full answer, but for those who want to fiddle... jsfiddle.net/LR5D9/3 this solution deals with the issue of prototype declarations messing up for var in x loops
  
  – unsynchronized
  Jul 13 '14 at 1:56
  
  

  
  
  
  

add a comment | 

I would like to get the keys of a JavaScript object as an array, either in jQuery or pure JavaScript.

Is there a less verbose way than this?

var foo = 'alpha' : 'puffin', 'beta' : 'beagle' ;
var keys = [];
for (var key in foo) 
 keys.push(key);

javascript ecmascript-5

share|improve this question

edited Jan 12 '18 at 21:45

dreftymac

16.4k2191154

asked Jan 6 '12 at 19:12

RichardRichard

10.9k2391141

var foo = 'alpha' : 'puffin', 'beta' : 'beagle' ;
var keys = [];
for (var key in foo) 
 keys.push(key);

share|improve this question

edited Jan 12 '18 at 21:45

dreftymac

16.4k2191154

asked Jan 6 '12 at 19:12

RichardRichard

10.9k2391141

share|improve this question

edited Jan 12 '18 at 21:45

dreftymac

16.4k2191154

asked Jan 6 '12 at 19:12

RichardRichard

10.9k2391141

edited Jan 12 '18 at 21:45

dreftymac

16.4k2191154

edited Jan 12 '18 at 21:45

dreftymac

16.4k2191154

asked Jan 6 '12 at 19:12

RichardRichard

10.9k2391141

asked Jan 6 '12 at 19:12

RichardRichard

10.9k2391141

7 Answers
7

active

oldest

votes

554

Use Object.keys:

var foo = 
 'alpha': 'puffin',
 'beta': 'beagle'
;

var keys = Object.keys(foo);
console.log(keys) // ['alpha', 'beta'] 
// (or maybe some other order, keys are unordered).

This is an ES5 feature. This means it works in all modern browsers but will not work in legacy browsers.

The ES5-shim has a implementation of Object.keys you can steal

share|improve this answer

edited 2 days ago

adiga

13.4k62745

answered Jan 6 '12 at 19:19

RaynosRaynos

135k43317374

• 
  
  
  

  
  5
  

  
  
  
  
  
  

  
  
  Note: This only works on modern browsers (by that I mean not IE < 9).
  
  – Rocket Hazmat
  Jan 6 '12 at 19:21
  

  
  
  
  


• 
  
  
  

  
  2
  

  
  
  
  
  
  

  
  
  And what about mobile browsers ?
  
  – Marwen Trabelsi
  Aug 7 '14 at 8:15
  
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  @SmartyTwiti: I'm not sure. I'd assume it does in like Chrome or Firefox.
  
  – Rocket Hazmat
  Aug 7 '14 at 15:17
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  MDN also has the above referred Polyfill, but notes bugs in IE7 and maybe 8, then refers off to a much shorter Polyfill here: tokenposts.blogspot.com.au/2012/04/…
  
  – Campbeln
  Jan 21 '15 at 23:17
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  This works in all mobile browsers Can I Use?
  
  – Edward Wall
  Jun 21 '18 at 5:44
  

  
  
  
  

 | 
show 1 more comment

59

You can use jQuery's $.map.

var foo = 'alpha' : 'puffin', 'beta' : 'beagle' ,
keys = $.map(foo, function(v, i)
 return i;
);

share|improve this answer

answered Jan 6 '12 at 19:18

Rocket HazmatRocket Hazmat

171k31248300

• 
  
  
  

  
  2
  

  
  
  
  
  
  

  
  
  This solution (Rocket's) works fine jsfiddle.net/KV3RA/3
  
  – MilkyWayJoe
  Jan 6 '12 at 19:41
  

  
  
  
  


• 
  
  
  

  
  3
  

  
  
  
  
  
  

  
  
  Seems to me this solution is much better if Object.keys() doesn't work in IE8...
  
  – NLemay
  Jan 10 '14 at 21:52
  

  
  
  
  

add a comment | 

30

Of course, Object.keys() is the best way to get an Object's keys. If it's not available in your environment, it can be trivially shimmed using code such as in your example (except you'd need to take into account your loop will iterate over all properties up the prototype chain, unlike Object.keys()'s behaviour).

However, your example code...

var foo = 'alpha' : 'puffin', 'beta' : 'beagle' ;
var keys = [];
for (var key in foo) 
 keys.push(key);

jsFiddle.

...could be modified. You can do the assignment right in the variable part.

var foo = 'alpha' : 'puffin', 'beta' : 'beagle' ;
var keys = [], i = 0;
for (keys[i++] in foo) 

jsFiddle.

Of course, this behaviour is different to what Object.keys() actually does (jsFiddle). You could simply use the shim on the MDN documentation.

share|improve this answer

answered Jun 8 '12 at 3:58

alexalex

348k173780916

• 
  
  
  

  
  8
  

  
  
  
  
  
  

  
  
  I liked this var keys = [], i = 0; for (keys[i++] in foo) +1
  
  – Jashwant
  Feb 1 '13 at 12:42
  
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  I heard that "for in" doesn't guarantee order, do you know if Object.keys does?
  
  – Chris Stephens
  May 13 '13 at 19:06
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  @ChrisStephens Neither guarantee order, even if the keys end up being in an ordered array.
  
  – alex
  May 13 '13 at 23:49
  

  
  
  
  


• 
  
  
  

  
  2
  

  
  
  
  
  
  

  
  
  all of these solutions need a hasOwnProperty() check, surely?
  
  – unsynchronized
  Jul 13 '14 at 0:38
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  @TIMINeutron There's no reason why it shouldn't :)
  
  – alex
  Dec 18 '14 at 22:31
  

  
  
  
  

 | 
show 5 more comments

6

I don't know about less verbose but I was inspired to coerce the following onto one line by the one-liner request, don't know how Pythonic it is though ;)

var keys = (function(o)var ks=[]; for(var k in o) ks.push(k); return ks)(foo);

share|improve this answer

answered Jan 6 '12 at 19:29

George JemptyGeorge Jempty

7,1151162133

• 
  
  
  

  
  3
  

  
  
  
  
  
  

  
  
  Maybe that should be var enumerableKeysOnThePrototypeChain ;)
  
  – alex
  May 13 '13 at 23:51
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  Maybe we're smart enough to know we don't have to worry about hasOwnProperty if the object is created entirely under our purview as opposed to being imported from somewhere else
  
  – George Jempty
  Jan 21 '16 at 17:35
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  not as pythonic as @alex's 2nd answer (for (keys[i++] in foo) ) though, because you're still performing Array.push() (not to mention declaring a whole function). A pythonic implementation should rely as much on implicit comprehension as possible, and failing that, using a lambda expression.
  
  – cowbert
  Sep 28 '17 at 21:10
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  @cowbert ok thanks for your observation
  
  – George Jempty
  Sep 29 '17 at 14:32
  

  
  
  
  

add a comment | 

1

Summary

For getting all of the keys of an Object you can use Object.keys(). Object.keys() takes an object as an argument and returns an array of all the keys.

Example:

const object = 
 a: 'string1',
 b: 42,
 c: 34
;

const keys = Object.keys(object)

console.log(keys);

console.log(keys.length) // we can easily access the total amount of properties the object has

In the above example we store an array of keys in the keys const. We then can easily access the amount of properties on the object by checking the length of the keys array.

Getting the values with: Object.values()

The complementary function of Object.keys() is Object.values(). This function takes an object as an argument and returns an array of values. For example:

const object = 
 a: 'random',
 b: 22,
 c: true
;


console.log(Object.values(object));

share|improve this answer

answered Aug 17 '18 at 8:39

Willem van der VeenWillem van der Veen

5,84133440

add a comment | 

1

If you decide to use Underscore.js you better do

var foo = 'alpha' : 'puffin', 'beta' : 'beagle' ;
var keys = [];
_.each( foo, function( val, key ) 
 keys.push(key);
);
console.log(keys);

share|improve this answer

answered Jan 9 at 6:04

mohammad javad ahmadimohammad javad ahmadi

150111

add a comment | 

1

In case you're here looking for something to list the keys of an n-depth nested object as a flat array:

const getObjectKeys = (obj, prefix = '') => 
 return Object.entries(obj).reduce((collector, [key, val]) => 
 const newKeys = [ ...collector, prefix ? `$prefix.$key` : key ]
 if (Object.prototype.toString.call(val) === '[object Object]') 
 const newPrefix = prefix ? `$prefix.$key` : key
 const otherKeys = getObjectKeys(val, newPrefix)
 return [ ...newKeys, ...otherKeys ]
 
 return newKeys
 , [])


console.log(getObjectKeys(a: 1, b: 2, c: d: 3, e: f: 4 ))

share|improve this answer

edited Mar 23 at 3:10

answered Mar 23 at 2:41

Cody MonizCody Moniz

2,16521617

add a comment | 

protected by Community♦ Jun 9 '17 at 6:53

Thank you for your interest in this question.
Because it has attracted low-quality or spam answers that had to be removed, posting an answer now requires 10 reputation on this site (the association bonus does not count).



Would you like to answer one of these unanswered questions instead?

554

Use Object.keys:

var foo = 
 'alpha': 'puffin',
 'beta': 'beagle'
;

var keys = Object.keys(foo);
console.log(keys) // ['alpha', 'beta'] 
// (or maybe some other order, keys are unordered).

This is an ES5 feature. This means it works in all modern browsers but will not work in legacy browsers.

The ES5-shim has a implementation of Object.keys you can steal

share|improve this answer

edited 2 days ago

adiga

13.4k62745

answered Jan 6 '12 at 19:19

RaynosRaynos

135k43317374

• 
  
  
  

  
  5
  

  
  
  
  
  
  

  
  
  Note: This only works on modern browsers (by that I mean not IE < 9).
  
  – Rocket Hazmat
  Jan 6 '12 at 19:21
  

  
  
  
  


• 
  
  
  

  
  2
  

  
  
  
  
  
  

  
  
  And what about mobile browsers ?
  
  – Marwen Trabelsi
  Aug 7 '14 at 8:15
  
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  @SmartyTwiti: I'm not sure. I'd assume it does in like Chrome or Firefox.
  
  – Rocket Hazmat
  Aug 7 '14 at 15:17
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  MDN also has the above referred Polyfill, but notes bugs in IE7 and maybe 8, then refers off to a much shorter Polyfill here: tokenposts.blogspot.com.au/2012/04/…
  
  – Campbeln
  Jan 21 '15 at 23:17
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  This works in all mobile browsers Can I Use?
  
  – Edward Wall
  Jun 21 '18 at 5:44
  

  
  
  
  

 | 
show 1 more comment

554

Use Object.keys:

var foo = 
 'alpha': 'puffin',
 'beta': 'beagle'
;

var keys = Object.keys(foo);
console.log(keys) // ['alpha', 'beta'] 
// (or maybe some other order, keys are unordered).

This is an ES5 feature. This means it works in all modern browsers but will not work in legacy browsers.

The ES5-shim has a implementation of Object.keys you can steal

share|improve this answer

edited 2 days ago

adiga

13.4k62745

answered Jan 6 '12 at 19:19

RaynosRaynos

135k43317374

• 
  
  
  

  
  5
  

  
  
  
  
  
  

  
  
  Note: This only works on modern browsers (by that I mean not IE < 9).
  
  – Rocket Hazmat
  Jan 6 '12 at 19:21
  

  
  
  
  


• 
  
  
  

  
  2
  

  
  
  
  
  
  

  
  
  And what about mobile browsers ?
  
  – Marwen Trabelsi
  Aug 7 '14 at 8:15
  
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  @SmartyTwiti: I'm not sure. I'd assume it does in like Chrome or Firefox.
  
  – Rocket Hazmat
  Aug 7 '14 at 15:17
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  MDN also has the above referred Polyfill, but notes bugs in IE7 and maybe 8, then refers off to a much shorter Polyfill here: tokenposts.blogspot.com.au/2012/04/…
  
  – Campbeln
  Jan 21 '15 at 23:17
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  This works in all mobile browsers Can I Use?
  
  – Edward Wall
  Jun 21 '18 at 5:44
  

  
  
  
  

 | 
show 1 more comment

Use Object.keys:

var foo = 
 'alpha': 'puffin',
 'beta': 'beagle'
;

var keys = Object.keys(foo);
console.log(keys) // ['alpha', 'beta'] 
// (or maybe some other order, keys are unordered).

This is an ES5 feature. This means it works in all modern browsers but will not work in legacy browsers.

The ES5-shim has a implementation of Object.keys you can steal

share|improve this answer

edited 2 days ago

adiga

13.4k62745

answered Jan 6 '12 at 19:19

RaynosRaynos

135k43317374

var foo = 
 'alpha': 'puffin',
 'beta': 'beagle'
;

var keys = Object.keys(foo);
console.log(keys) // ['alpha', 'beta'] 
// (or maybe some other order, keys are unordered).

var foo = 
 'alpha': 'puffin',
 'beta': 'beagle'
;

var keys = Object.keys(foo);
console.log(keys) // ['alpha', 'beta'] 
// (or maybe some other order, keys are unordered).

var foo = 
 'alpha': 'puffin',
 'beta': 'beagle'
;

var keys = Object.keys(foo);
console.log(keys) // ['alpha', 'beta'] 
// (or maybe some other order, keys are unordered).

share|improve this answer

edited 2 days ago

adiga

13.4k62745

answered Jan 6 '12 at 19:19

RaynosRaynos

135k43317374

edited 2 days ago

adiga

13.4k62745

edited 2 days ago

adiga

13.4k62745

answered Jan 6 '12 at 19:19

RaynosRaynos

135k43317374

answered Jan 6 '12 at 19:19

RaynosRaynos

135k43317374

59

You can use jQuery's $.map.

var foo = 'alpha' : 'puffin', 'beta' : 'beagle' ,
keys = $.map(foo, function(v, i)
 return i;
);

share|improve this answer

answered Jan 6 '12 at 19:18

Rocket HazmatRocket Hazmat

171k31248300

• 
  
  
  

  
  2
  

  
  
  
  
  
  

  
  
  This solution (Rocket's) works fine jsfiddle.net/KV3RA/3
  
  – MilkyWayJoe
  Jan 6 '12 at 19:41
  

  
  
  
  


• 
  
  
  

  
  3
  

  
  
  
  
  
  

  
  
  Seems to me this solution is much better if Object.keys() doesn't work in IE8...
  
  – NLemay
  Jan 10 '14 at 21:52
  

  
  
  
  

add a comment | 

59

You can use jQuery's $.map.

var foo = 'alpha' : 'puffin', 'beta' : 'beagle' ,
keys = $.map(foo, function(v, i)
 return i;
);

share|improve this answer

answered Jan 6 '12 at 19:18

Rocket HazmatRocket Hazmat

171k31248300

• 
  
  
  

  
  2
  

  
  
  
  
  
  

  
  
  This solution (Rocket's) works fine jsfiddle.net/KV3RA/3
  
  – MilkyWayJoe
  Jan 6 '12 at 19:41
  

  
  
  
  


• 
  
  
  

  
  3
  

  
  
  
  
  
  

  
  
  Seems to me this solution is much better if Object.keys() doesn't work in IE8...
  
  – NLemay
  Jan 10 '14 at 21:52
  

  
  
  
  

add a comment | 

You can use jQuery's $.map.

var foo = 'alpha' : 'puffin', 'beta' : 'beagle' ,
keys = $.map(foo, function(v, i)
 return i;
);

share|improve this answer

answered Jan 6 '12 at 19:18

Rocket HazmatRocket Hazmat

171k31248300

var foo = 'alpha' : 'puffin', 'beta' : 'beagle' ,
keys = $.map(foo, function(v, i)
 return i;
);

share|improve this answer

answered Jan 6 '12 at 19:18

Rocket HazmatRocket Hazmat

171k31248300

answered Jan 6 '12 at 19:18

Rocket HazmatRocket Hazmat

171k31248300

answered Jan 6 '12 at 19:18

Rocket HazmatRocket Hazmat

171k31248300

30

Of course, Object.keys() is the best way to get an Object's keys. If it's not available in your environment, it can be trivially shimmed using code such as in your example (except you'd need to take into account your loop will iterate over all properties up the prototype chain, unlike Object.keys()'s behaviour).

However, your example code...

var foo = 'alpha' : 'puffin', 'beta' : 'beagle' ;
var keys = [];
for (var key in foo) 
 keys.push(key);

jsFiddle.

...could be modified. You can do the assignment right in the variable part.

var foo = 'alpha' : 'puffin', 'beta' : 'beagle' ;
var keys = [], i = 0;
for (keys[i++] in foo) 

jsFiddle.

Of course, this behaviour is different to what Object.keys() actually does (jsFiddle). You could simply use the shim on the MDN documentation.

share|improve this answer

answered Jun 8 '12 at 3:58

alexalex

348k173780916

• 
  
  
  

  
  8
  

  
  
  
  
  
  

  
  
  I liked this var keys = [], i = 0; for (keys[i++] in foo) +1
  
  – Jashwant
  Feb 1 '13 at 12:42
  
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  I heard that "for in" doesn't guarantee order, do you know if Object.keys does?
  
  – Chris Stephens
  May 13 '13 at 19:06
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  @ChrisStephens Neither guarantee order, even if the keys end up being in an ordered array.
  
  – alex
  May 13 '13 at 23:49
  

  
  
  
  


• 
  
  
  

  
  2
  

  
  
  
  
  
  

  
  
  all of these solutions need a hasOwnProperty() check, surely?
  
  – unsynchronized
  Jul 13 '14 at 0:38
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  @TIMINeutron There's no reason why it shouldn't :)
  
  – alex
  Dec 18 '14 at 22:31
  

  
  
  
  

 | 
show 5 more comments

30

Of course, Object.keys() is the best way to get an Object's keys. If it's not available in your environment, it can be trivially shimmed using code such as in your example (except you'd need to take into account your loop will iterate over all properties up the prototype chain, unlike Object.keys()'s behaviour).

However, your example code...

var foo = 'alpha' : 'puffin', 'beta' : 'beagle' ;
var keys = [];
for (var key in foo) 
 keys.push(key);

jsFiddle.

...could be modified. You can do the assignment right in the variable part.

var foo = 'alpha' : 'puffin', 'beta' : 'beagle' ;
var keys = [], i = 0;
for (keys[i++] in foo) 

jsFiddle.

Of course, this behaviour is different to what Object.keys() actually does (jsFiddle). You could simply use the shim on the MDN documentation.

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answered Jun 8 '12 at 3:58

alexalex

348k173780916

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  I liked this var keys = [], i = 0; for (keys[i++] in foo) +1
  
  – Jashwant
  Feb 1 '13 at 12:42
  
  

  
  
  
  


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  I heard that "for in" doesn't guarantee order, do you know if Object.keys does?
  
  – Chris Stephens
  May 13 '13 at 19:06
  

  
  
  
  


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  @ChrisStephens Neither guarantee order, even if the keys end up being in an ordered array.
  
  – alex
  May 13 '13 at 23:49
  

  
  
  
  


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  all of these solutions need a hasOwnProperty() check, surely?
  
  – unsynchronized
  Jul 13 '14 at 0:38
  

  
  
  
  


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  @TIMINeutron There's no reason why it shouldn't :)
  
  – alex
  Dec 18 '14 at 22:31
  

  
  
  
  

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show 5 more comments

Of course, Object.keys() is the best way to get an Object's keys. If it's not available in your environment, it can be trivially shimmed using code such as in your example (except you'd need to take into account your loop will iterate over all properties up the prototype chain, unlike Object.keys()'s behaviour).

However, your example code...

var foo = 'alpha' : 'puffin', 'beta' : 'beagle' ;
var keys = [];
for (var key in foo) 
 keys.push(key);

jsFiddle.

...could be modified. You can do the assignment right in the variable part.

var foo = 'alpha' : 'puffin', 'beta' : 'beagle' ;
var keys = [], i = 0;
for (keys[i++] in foo) 

jsFiddle.

Of course, this behaviour is different to what Object.keys() actually does (jsFiddle). You could simply use the shim on the MDN documentation.

share|improve this answer

answered Jun 8 '12 at 3:58

alexalex

348k173780916

var foo = 'alpha' : 'puffin', 'beta' : 'beagle' ;
var keys = [];
for (var key in foo) 
 keys.push(key);

var foo = 'alpha' : 'puffin', 'beta' : 'beagle' ;
var keys = [], i = 0;
for (keys[i++] in foo) 

share|improve this answer

answered Jun 8 '12 at 3:58

alexalex

348k173780916

answered Jun 8 '12 at 3:58

alexalex

348k173780916

answered Jun 8 '12 at 3:58

alexalex

348k173780916

6

I don't know about less verbose but I was inspired to coerce the following onto one line by the one-liner request, don't know how Pythonic it is though ;)

var keys = (function(o)var ks=[]; for(var k in o) ks.push(k); return ks)(foo);

share|improve this answer

answered Jan 6 '12 at 19:29

George JemptyGeorge Jempty

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  Maybe that should be var enumerableKeysOnThePrototypeChain ;)
  
  – alex
  May 13 '13 at 23:51
  

  
  
  
  


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  Maybe we're smart enough to know we don't have to worry about hasOwnProperty if the object is created entirely under our purview as opposed to being imported from somewhere else
  
  – George Jempty
  Jan 21 '16 at 17:35
  

  
  
  
  


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  not as pythonic as @alex's 2nd answer (for (keys[i++] in foo) ) though, because you're still performing Array.push() (not to mention declaring a whole function). A pythonic implementation should rely as much on implicit comprehension as possible, and failing that, using a lambda expression.
  
  – cowbert
  Sep 28 '17 at 21:10
  

  
  
  
  


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  @cowbert ok thanks for your observation
  
  – George Jempty
  Sep 29 '17 at 14:32
  

  
  
  
  

add a comment | 

6

I don't know about less verbose but I was inspired to coerce the following onto one line by the one-liner request, don't know how Pythonic it is though ;)

var keys = (function(o)var ks=[]; for(var k in o) ks.push(k); return ks)(foo);

share|improve this answer

answered Jan 6 '12 at 19:29

George JemptyGeorge Jempty

7,1151162133

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  3
  

  
  
  
  
  
  

  
  
  Maybe that should be var enumerableKeysOnThePrototypeChain ;)
  
  – alex
  May 13 '13 at 23:51
  

  
  
  
  


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  1
  

  
  
  
  
  
  

  
  
  Maybe we're smart enough to know we don't have to worry about hasOwnProperty if the object is created entirely under our purview as opposed to being imported from somewhere else
  
  – George Jempty
  Jan 21 '16 at 17:35
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  not as pythonic as @alex's 2nd answer (for (keys[i++] in foo) ) though, because you're still performing Array.push() (not to mention declaring a whole function). A pythonic implementation should rely as much on implicit comprehension as possible, and failing that, using a lambda expression.
  
  – cowbert
  Sep 28 '17 at 21:10
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  @cowbert ok thanks for your observation
  
  – George Jempty
  Sep 29 '17 at 14:32
  

  
  
  
  

add a comment | 

I don't know about less verbose but I was inspired to coerce the following onto one line by the one-liner request, don't know how Pythonic it is though ;)

var keys = (function(o)var ks=[]; for(var k in o) ks.push(k); return ks)(foo);

share|improve this answer

answered Jan 6 '12 at 19:29

George JemptyGeorge Jempty

7,1151162133

var keys = (function(o)var ks=[]; for(var k in o) ks.push(k); return ks)(foo);

share|improve this answer

answered Jan 6 '12 at 19:29

George JemptyGeorge Jempty

7,1151162133

answered Jan 6 '12 at 19:29

George JemptyGeorge Jempty

7,1151162133

answered Jan 6 '12 at 19:29

George JemptyGeorge Jempty

7,1151162133

1

Summary

For getting all of the keys of an Object you can use Object.keys(). Object.keys() takes an object as an argument and returns an array of all the keys.

Example:

const object = 
 a: 'string1',
 b: 42,
 c: 34
;

const keys = Object.keys(object)

console.log(keys);

console.log(keys.length) // we can easily access the total amount of properties the object has

In the above example we store an array of keys in the keys const. We then can easily access the amount of properties on the object by checking the length of the keys array.

Getting the values with: Object.values()

The complementary function of Object.keys() is Object.values(). This function takes an object as an argument and returns an array of values. For example:

const object = 
 a: 'random',
 b: 22,
 c: true
;


console.log(Object.values(object));

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answered Aug 17 '18 at 8:39

Willem van der VeenWillem van der Veen

5,84133440

add a comment |