How to list the properties of a JavaScript object

Question

Say I create an object thus   var myObject             ircEvent    PRIVMSG    method    newURI    regex     http           What is the best way to retrieve a list of the property names  i e  I would like to end up with some variable  keys  such that   keys      ircEvent    method    regex

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Since I use underscore js in almost every project  I would use the keys function   var obj    name   gach   hello   world    console log   keys obj      The output of that will be     name    hello

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Building on the accepted answer    If the Object has properties you want to call say  properties   try   var keys   Object keys myJSONObject    for  var j 0  j  lt  keys length  j        Object keys j   properties

User · Answer

With ES6 and later  ECMAScript 2015   you can get all properties like this  let keys   Object keys myObject    And if you wanna list out all values  let values   Object keys myObject  map key   gt  myObject key

User · Answer

Object getOwnPropertyNames obj   This function also shows non-enumerable properties in addition to those shown by Object keys obj    In JS  every property has a few properties  including a boolean enumerable   In general  non-enumerable properties are more  internalish  and less often used  but it is insightful to look into them sometimes to see what is really going on   Example   var o   Object create  base 0   Object defineProperty o   yes    enumerable  true   Object defineProperty o   not    enumerable  false    console log Object getOwnPropertyNames o         yes    not     console log Object keys o         yes     for  var x in o      console log x     yes  base   Also note how    Object getOwnPropertyNames and Object keys don t go up the prototype chain to find base for in does   More about the prototype chain here  https   stackoverflow com a 23877420 895245

User · Answer

Could do it with jQuery as follows   var objectKeys     map object  function value  key      return key

User · Answer

Since I use underscore js in almost every project  I would use the keys function   var obj    name   gach   hello   world    console log   keys obj      The output of that will be     name    hello

User · Answer

As slashnick pointed out  you can use the  for in  construct to iterate over an object for its attribute names  However you ll be iterating over all attribute names in the object s prototype chain  If you want to iterate only over the object s own attributes  you can make use of the Object hasOwnProperty   method  Thus having the following   for  var key in obj        if  obj hasOwnProperty key                useful code here

User · Answer

As slashnick pointed out  you can use the  for in  construct to iterate over an object for its attribute names  However you ll be iterating over all attribute names in the object s prototype chain  If you want to iterate only over the object s own attributes  you can make use of the Object hasOwnProperty   method  Thus having the following   for  var key in obj        if  obj hasOwnProperty key                useful code here

User · Answer

Under browsers supporting js 1 8    i for i in obj

User · Answer

The solution work on my cases and cross-browser   var getKeys   function obj        var type   typeof  obj      var isObjectType   type      function     type      object       obj          1     if isObjectType            return Object keys obj                 2     var keys           for var i in obj            if obj hasOwnProperty i                 keys push i                      if keys length            return keys                3 - bug for ie9  lt      var hasEnumbug     toString  null  propertyIsEnumerable  toString        if hasEnumbug            var nonEnumerableProps     valueOf    isPrototypeOf    toString                propertyIsEnumerable    hasOwnProperty    toLocaleString             var nonEnumIdx   nonEnumerableProps length           while  nonEnumIdx--                var prop   nonEnumerableProps nonEnumIdx               if  Object prototype hasOwnProperty call obj  prop                     keys push prop                                       return keys

User · Answer

The solution work on my cases and cross-browser   var getKeys   function obj        var type   typeof  obj      var isObjectType   type      function     type      object       obj          1     if isObjectType            return Object keys obj                 2     var keys           for var i in obj            if obj hasOwnProperty i                 keys push i                      if keys length            return keys                3 - bug for ie9  lt      var hasEnumbug     toString  null  propertyIsEnumerable  toString        if hasEnumbug            var nonEnumerableProps     valueOf    isPrototypeOf    toString                propertyIsEnumerable    hasOwnProperty    toLocaleString             var nonEnumIdx   nonEnumerableProps length           while  nonEnumIdx--                var prop   nonEnumerableProps nonEnumIdx               if  Object prototype hasOwnProperty call obj  prop                     keys push prop                                       return keys

User · Answer

With ES6 and later  ECMAScript 2015   you can get all properties like this  let keys   Object keys myObject    And if you wanna list out all values  let values   Object keys myObject  map key   gt  myObject key

User · Answer

In modern browsers  IE9   FF4   Chrome5   Opera12   Safari5   you can use the built in Object keys method  var keys   Object keys myObject    The above has a full polyfill but a simplified version is  var getKeys   function obj      var keys          for var key in obj         keys push key           return keys     Alternatively replace var getKeys with Object prototype keys to allow you to call  keys   on any object   Extending the prototype has some side effects and I wouldn t recommend doing it

User · Answer

I m a huge fan of the dump function   http   ajaxian com archives javascript-variable-dump-in-coldfusion

User · Answer

Mozilla has full implementation details on how to do it in a browser where it isn t supported  if that helps   if   Object keys      Object keys    function          var hasOwnProperty   Object prototype hasOwnProperty          hasDontEnumBug      toString  null   propertyIsEnumerable  toString            dontEnums                toString              toLocaleString              valueOf              hasOwnProperty              isPrototypeOf              propertyIsEnumerable              constructor                     dontEnumsLength   dontEnums length       return function  obj          if  typeof obj      object   amp  amp  typeof obj      function     obj     null  throw new TypeError  Object keys called on non-object           var result              for  var prop in obj            if  hasOwnProperty call obj  prop   result push prop                  if  hasDontEnumBug            for  var i 0  i  lt  dontEnumsLength  i                if  hasOwnProperty call obj  dontEnums i    result push dontEnums i                            return result                     You could include it however you d like  but possibly in some kind of extensions js file at the top of your script stack

User · Answer

In modern browsers  IE9   FF4   Chrome5   Opera12   Safari5   you can use the built in Object keys method  var keys   Object keys myObject    The above has a full polyfill but a simplified version is  var getKeys   function obj      var keys          for var key in obj         keys push key           return keys     Alternatively replace var getKeys with Object prototype keys to allow you to call  keys   on any object   Extending the prototype has some side effects and I wouldn t recommend doing it

User · Answer

Under browsers supporting js 1 8    i for i in obj

User · Answer

In modern browsers  IE9   FF4   Chrome5   Opera12   Safari5   you can use the built in Object keys method  var keys   Object keys myObject    The above has a full polyfill but a simplified version is  var getKeys   function obj      var keys          for var key in obj         keys push key           return keys     Alternatively replace var getKeys with Object prototype keys to allow you to call  keys   on any object   Extending the prototype has some side effects and I wouldn t recommend doing it

User · Answer

Use Reflect ownKeys    var obj    a  1  b  2  c  3   Reflect ownKeys obj       a    b    c     Object keys and Object getOwnPropertyNames cannot get non-enumerable properties  It s working even for non-enumerable properties   var obj    a  1  b  2  c  3   obj Symbol      4  Reflect ownKeys obj       a    b    c   Symbol

User · Answer

Building on the accepted answer    If the Object has properties you want to call say  properties   try   var keys   Object keys myJSONObject    for  var j 0  j  lt  keys length  j        Object keys j   properties

User · Answer

Note that Object keys and other ECMAScript 5 methods are supported by Firefox 4  Chrome 6  Safari 5  IE 9 and above   For example    var o     foo   1   bar   2    alert Object keys o      ECMAScript 5 compatibility table  http   kangax github com es5-compat-table   Description of new methods  http   markcaudill com index php 2009 04 javascript-new-features-ecma5

User · Answer

I m a huge fan of the dump function   http   ajaxian com archives javascript-variable-dump-in-coldfusion

User · Answer

IE does not support for i in obj  for native properties  Here is a list of all the props I could find   It seems stackoverflow does some stupid filtering   The list is available at the bottom of this google group post - https   groups google com group hackvertor browse thread thread a9ba81ca642a63e0

User · Answer

As Sam Dutton answered  a new method for this very purpose has been introduced in ECMAScript 5th Edition   Object keys   will do what you want and is supported in Firefox 4  Chrome 6  Safari 5 and IE 9  You can also very easily implement the method in browsers that don t support it   However  some of the implementations out there aren t fully compatible with Internet Explorer   Here s a more compatible solution  Object keys   Object keys     function          var hasOwnProperty   Object prototype hasOwnProperty          hasDontEnumBug     toString null  propertyIsEnumerable  quot toString quot            DontEnums                   toString    toLocaleString    valueOf    hasOwnProperty                isPrototypeOf    propertyIsEnumerable    constructor                     DontEnumsLength   DontEnums length               return function  o            if  typeof o     quot object quot   amp  amp  typeof o     quot function quot     o     null              throw new TypeError  quot Object keys called on a non-object quot                 var result               for  var name in o                if  hasOwnProperty call o  name                   result push name                          if  hasDontEnumBug                for  var i   0  i  lt  DontEnumsLength  i                      if  hasOwnProperty call o  DontEnums i                        result push DontEnums i                                            return result                Note that the currently accepted answer doesn t include a check for hasOwnProperty   and will return properties that are inherited through the prototype chain   It also doesn t account for the famous DontEnum bug in Internet Explorer where non-enumerable properties on the prototype chain cause locally declared properties with the same name to inherit their DontEnum attribute  Implementing Object keys   will give you a more robust solution  EDIT  following a recent discussion with kangax  a well-known contributor to Prototype  I implemented the workaround for the DontEnum bug based on code for his Object forIn   function found here

User · Answer

This will work in most browsers  even in IE8   and no libraries of any sort are required   var i is your key   var myJSONObject      ircEvent    PRIVMSG    method    newURI    regex     http          var keys     for  var i in myJSONObject     keys push i     alert keys

User · Answer

Object getOwnPropertyNames obj   This function also shows non-enumerable properties in addition to those shown by Object keys obj    In JS  every property has a few properties  including a boolean enumerable   In general  non-enumerable properties are more  internalish  and less often used  but it is insightful to look into them sometimes to see what is really going on   Example   var o   Object create  base 0   Object defineProperty o   yes    enumerable  true   Object defineProperty o   not    enumerable  false    console log Object getOwnPropertyNames o         yes    not     console log Object keys o         yes     for  var x in o      console log x     yes  base   Also note how    Object getOwnPropertyNames and Object keys don t go up the prototype chain to find base for in does   More about the prototype chain here  https   stackoverflow com a 23877420 895245

User · Answer

Could do it with jQuery as follows   var objectKeys     map object  function value  key      return key

User · Answer

In modern browsers  IE9   FF4   Chrome5   Opera12   Safari5   you can use the built in Object keys method  var keys   Object keys myObject    The above has a full polyfill but a simplified version is  var getKeys   function obj      var keys          for var key in obj         keys push key           return keys     Alternatively replace var getKeys with Object prototype keys to allow you to call  keys   on any object   Extending the prototype has some side effects and I wouldn t recommend doing it

User · Answer

Note that Object keys and other ECMAScript 5 methods are supported by Firefox 4  Chrome 6  Safari 5  IE 9 and above   For example    var o     foo   1   bar   2    alert Object keys o      ECMAScript 5 compatibility table  http   kangax github com es5-compat-table   Description of new methods  http   markcaudill com index php 2009 04 javascript-new-features-ecma5

User · Answer

if you are trying to get the elements only but not the functions then this code can help you  this getKeys   function          var keys   new Array        for var key in this             if  typeof this key       function                  keys push key                       return keys      this is part of my implementation of the HashMap and I only want the keys   this  is the hashmap object that contains the keys

User · Answer

Mozilla has full implementation details on how to do it in a browser where it isn t supported  if that helps   if   Object keys      Object keys    function          var hasOwnProperty   Object prototype hasOwnProperty          hasDontEnumBug      toString  null   propertyIsEnumerable  toString            dontEnums                toString              toLocaleString              valueOf              hasOwnProperty              isPrototypeOf              propertyIsEnumerable              constructor                     dontEnumsLength   dontEnums length       return function  obj          if  typeof obj      object   amp  amp  typeof obj      function     obj     null  throw new TypeError  Object keys called on non-object           var result              for  var prop in obj            if  hasOwnProperty call obj  prop   result push prop                  if  hasDontEnumBug            for  var i 0  i  lt  dontEnumsLength  i                if  hasOwnProperty call obj  dontEnums i    result push dontEnums i                            return result                     You could include it however you d like  but possibly in some kind of extensions js file at the top of your script stack

User · Answer

This will work in most browsers  even in IE8   and no libraries of any sort are required   var i is your key   var myJSONObject      ircEvent    PRIVMSG    method    newURI    regex     http          var keys     for  var i in myJSONObject     keys push i     alert keys

User · Answer

Use Reflect ownKeys    var obj    a  1  b  2  c  3   Reflect ownKeys obj       a    b    c     Object keys and Object getOwnPropertyNames cannot get non-enumerable properties  It s working even for non-enumerable properties   var obj    a  1  b  2  c  3   obj Symbol      4  Reflect ownKeys obj       a    b    c   Symbol

User · Answer

As slashnick pointed out  you can use the  for in  construct to iterate over an object for its attribute names  However you ll be iterating over all attribute names in the object s prototype chain  If you want to iterate only over the object s own attributes  you can make use of the Object hasOwnProperty   method  Thus having the following   for  var key in obj        if  obj hasOwnProperty key                useful code here

User · Answer

As slashnick pointed out  you can use the  for in  construct to iterate over an object for its attribute names  However you ll be iterating over all attribute names in the object s prototype chain  If you want to iterate only over the object s own attributes  you can make use of the Object hasOwnProperty   method  Thus having the following   for  var key in obj        if  obj hasOwnProperty key                useful code here

User · Answer

As Sam Dutton answered  a new method for this very purpose has been introduced in ECMAScript 5th Edition   Object keys   will do what you want and is supported in Firefox 4  Chrome 6  Safari 5 and IE 9  You can also very easily implement the method in browsers that don t support it   However  some of the implementations out there aren t fully compatible with Internet Explorer   Here s a more compatible solution  Object keys   Object keys     function          var hasOwnProperty   Object prototype hasOwnProperty          hasDontEnumBug     toString null  propertyIsEnumerable  quot toString quot            DontEnums                   toString    toLocaleString    valueOf    hasOwnProperty                isPrototypeOf    propertyIsEnumerable    constructor                     DontEnumsLength   DontEnums length               return function  o            if  typeof o     quot object quot   amp  amp  typeof o     quot function quot     o     null              throw new TypeError  quot Object keys called on a non-object quot                 var result               for  var name in o                if  hasOwnProperty call o  name                   result push name                          if  hasDontEnumBug                for  var i   0  i  lt  DontEnumsLength  i                      if  hasOwnProperty call o  DontEnums i                        result push DontEnums i                                            return result                Note that the currently accepted answer doesn t include a check for hasOwnProperty   and will return properties that are inherited through the prototype chain   It also doesn t account for the famous DontEnum bug in Internet Explorer where non-enumerable properties on the prototype chain cause locally declared properties with the same name to inherit their DontEnum attribute  Implementing Object keys   will give you a more robust solution  EDIT  following a recent discussion with kangax  a well-known contributor to Prototype  I implemented the workaround for the DontEnum bug based on code for his Object forIn   function found here

User · Answer

IE does not support for i in obj  for native properties  Here is a list of all the props I could find   It seems stackoverflow does some stupid filtering   The list is available at the bottom of this google group post - https   groups google com group hackvertor browse thread thread a9ba81ca642a63e0

User · Answer

if you are trying to get the elements only but not the functions then this code can help you  this getKeys   function          var keys   new Array        for var key in this             if  typeof this key       function                  keys push key                       return keys      this is part of my implementation of the HashMap and I only want the keys   this  is the hashmap object that contains the keys

[javascript] How to list the properties of a JavaScript object?

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