Getting JavaScript object key list

Question

I have a JavaScript object like  var obj        key1   value1      key2   value2      key3   value3      key4   value4      How can I get the length and list of keys in this object

User · Answer

Use Object keys      it s the way to go   Full documentation is available on the MDN site linked below   https   developer mozilla org en-US docs Web JavaScript Reference Global Objects Object keys

User · Answer

var keys   new Array    for var key in obj       keys keys length    key     var keyLength   keys length    to access any value from the object  you can use obj key

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If you only want the keys which are specific to that particular object and not any derived prototype properties   function getKeys obj        var r          for  var k in obj            if   obj hasOwnProperty k                continue         r push k            return r     e g   var keys   getKeys   eggs   null   spam   true   var length   keys length    access the  length  property as usual for arrays

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Recursive solution for browsers that support ECMAScript 5   var getObjectKeys   function obj        var keys   Object keys obj       var length   keys length       if  length     0            for  var i   0  i  lt  length  i                  if  typeof obj keys i        object                     keys keys i     getObjectKeys obj keys i                                        return keys

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obj     a   c   b   d     You can try     index for  index in obj      this will return     a   b     to get the list of keys or    obj index  for  index in obj     to get the values

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Anurags answer is basically correct  But to support Object keys obj  in older browsers as well you can use the code below that is copied from  https   developer mozilla org en-US docs Web JavaScript Reference Global Objects Object keys   It adds the Object keys obj  method if it s not available from the browser   if   Object keys     Object keys    function       use strict    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       prop  i     for  prop in obj        if  hasOwnProperty call obj  prop           result push prop                if  hasDontEnumBug        for  i   0  i  lt  dontEnumsLength  i            if  hasOwnProperty call obj  dontEnums i              result push dontEnums i                        return result

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if props userType             var data                Object keys props userType  map i  gt                   data push props userType i                          setService data

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var obj        key1   value1      key2   value2      key3   value3      key4   value4     console log Object keys obj    console log Object keys obj  length

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x000D   x000D  var obj       key1   value1     key2   value2     key3   value3     key4   value4     var keys        for  var k in obj  keys push k    console log  total     keys length     keys      keys   x000D   x000D   x000D

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For a comma-delineated string listing the keys of a JSON Object  try the following   function listKeys jObj       var keyString           for var k in jObj           keyString       k             return keyString slice 1           listKeys   a     foo    b     foo    c     foo    - gt   a b c

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Using ES6   you can use forEach to iterate over the Keys of an Object  To get all the keys you can use Object keys which returns all the keys in an Object  Object keys obj  forEach function keyValue  index  map       console log keyValue          Short hand of the above snippet would be  which only takes one parameter  Object keys obj  forEach function keyValue       console log keyValue

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using slice  apply and join method   var print   Array prototype slice apply  obj    alert  length   print length   list  print join

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x000D   x000D  var obj     x000D     key1   value1   x000D     key2   value2   x000D     key3   value3   x000D     key4   value4  x000D    x000D  var keys   Object keys obj   x000D  console log  obj contains     keys length     keys      keys   x000D   x000D   x000D    It s supported on most major browsers now

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If you decide to use Underscore js you better do  var obj         key1   value1       key2   value2       key3   value3       key4   value4     var keys         each  obj  function  val  key         keys push key       console log keys lenth  keys

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In JavaScript  an object is a standalone entity  with properties and type   For fetching values from Object in form of array   Object values obj     obj is object name that you used  Result -     value1    value2    value3    value4    For fetching keys from Object in form of array   Object keys obj     obj is object name that you used  Result -    key1    key2    key3    key4    As both functions are returning array you can get the length of keys or value by using length property  For instance -  Object values obj  length or Object keys obj  length

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Note that in coffeescript this can be accomplished in all browsers and node as  k for k of obj   and thus   1 for   of obj  length

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Underscore js makes the transformation pretty clean   var keys     map x  function v  k    return k        Edit  I missed that you can do this too   var keys     keys x

[javascript] Getting JavaScript object key list

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