Is object empty

Question

What is the fastest way to check if an object is empty or not   Is there a faster and better way than this   function count obj obj       var i   0      for var key in obj             i             return i

User · Answer

Imagine you have the objects below   var obj1      var obj2   test   test      Don t forget we can NOT use     sign for testing an object equality as they get  inheritance  so If you using ECMA 5 and upper version of javascript  the answer is easy  you can use the function below   function isEmpty obj         check if it s an Obj first    var isObj   obj     null      amp  amp  typeof obj      object       amp  amp  Object prototype toString call obj        object Object        if  isObj           for  var o in obj               if  obj hasOwnProperty o                    return false                 break                               return true       else          console error  isEmpty function only accept an Object             so the result as below   isEmpty obj1     this returns true isEmpty obj2     this returns false isEmpty         log in console  isEmpty function only accept an Object

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I modified Sean Vieira s code to suit my needs  null and undefined don t count as object at all  and numbers  boolean values and empty strings return false     x000D   x000D   use strict   x000D   x000D     Speed up calls to hasOwnProperty x000D  var hasOwnProperty   Object prototype hasOwnProperty  x000D   x000D  var isObjectEmpty   function obj    x000D         null and undefined are not empty x000D      if  obj    null  return false  x000D      if obj     false  return false  x000D      if obj     true  return false  x000D      if obj         return false  x000D   x000D      if typeof obj      number     x000D          return false  x000D           x000D       x000D         Assume if it has a length property with a non-zero value x000D         that that property is correct  x000D      if  obj length  gt  0     return false  x000D      if  obj length     0   return true  x000D   x000D         Otherwise  does it have any properties of its own  x000D         Note that this doesn t handle x000D         toString and valueOf enumeration bugs in IE  lt  9 x000D      for  var key in obj    x000D          if  hasOwnProperty call obj  key   return false  x000D        x000D       x000D       x000D       x000D      return true  x000D     x000D   x000D  exports isObjectEmpty   isObjectEmpty  x000D   x000D   x000D

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Lets put this baby to bed  tested under Node  Chrome  Firefox and IE 9  it becomes evident that for most use cases     for   in     is the fastest option to use  Object keys obj  length is 10 times slower for empty objects JSON stringify obj  length is always the slowest  not surprising  Object getOwnPropertyNames obj  length takes longer than Object keys obj  length can be much longer on some systems    Bottom line performance wise  use   function isEmpty obj        for  var x in obj    return false       return true      or       function isEmpty obj       for  var x in obj    if  obj hasOwnProperty x    return false       return true      Results under Node     first result   return  Object keys obj  length     0  second result  for  var x in obj    return false       third result   for  var x in obj    if  obj hasOwnProperty x    return false       forth result   return           JSON stringify obj     Testing for Object with 0 keys 0 00018 0 000015 0 000015 0 000324  Testing for Object with 1 keys 0 000346 0 000458 0 000577 0 000657  Testing for Object with 2 keys 0 000375 0 00046 0 000565 0 000773  Testing for Object with 3 keys 0 000406 0 000476 0 000577 0 000904  Testing for Object with 4 keys 0 000435 0 000487 0 000589 0 001031  Testing for Object with 5 keys 0 000465 0 000501 0 000604 0 001148  Testing for Object with 6 keys 0 000492 0 000511 0 000618 0 001269  Testing for Object with 7 keys 0 000528 0 000527 0 000637 0 00138  Testing for Object with 8 keys 0 000565 0 000538 0 000647 0 00159  Testing for Object with 100 keys 0 003718 0 00243 0 002535 0 01381  Testing for Object with 1000 keys 0 0337 0 0193 0 0194 0 1337  Note that if your typical use case tests a non empty object with few keys  and rarely do you get to test empty objects or objects with 10 or more keys  consider the Object keys obj  length option  - otherwise go with the more generic  for    in     implementation   Note that Firefox seem to have a faster support for Object keys obj  length and Object getOwnPropertyNames obj  length  making it a better choice for any non empty Object  but still when it comes to empty objects  the  for   in     is simply 10 times faster   My 2 cents is that  Object keys obj  length is a poor idea since it creates an object of keys just to count how many keys are inside  than destroys it  In order to create that object he needs to loop overt the keys    so why use it and not the  for    in     option      x000D   x000D  var a       x000D   x000D  function timeit func count    x000D     if   count  count   100000  x000D     var start   Date now    x000D     for  i 0 i lt count i    func    x000D     var end   Date now    x000D     var duration   end - start  x000D     console log duration count  x000D    x000D   x000D  function isEmpty1     x000D      return  Object keys a  length     0  x000D    x000D  function isEmpty2     x000D      for  x in a    return false    x000D      return true  x000D    x000D  function isEmpty3     x000D      for  x in a    if  a hasOwnProperty x    return false    x000D      return true  x000D    x000D  function isEmpty4     x000D      return           JSON stringify a   x000D    x000D   x000D   x000D  for  var j 0 j lt 10 j      x000D     a      x000D     for  var i 0 i lt j i    a i    i  x000D     console log  Testing for Object with   Object keys a  length   keys   x000D     timeit isEmpty1   x000D     timeit isEmpty2   x000D     timeit isEmpty3   x000D     timeit isEmpty4   x000D    x000D   x000D  a      x000D  for  var i 0 i lt 100 i    a i    i  x000D  console log  Testing for Object with   Object keys a  length   keys   x000D  timeit isEmpty1   x000D  timeit isEmpty2   x000D  timeit isEmpty3   x000D  timeit isEmpty4  10000   x000D   x000D  a      x000D  for  var i 0 i lt 1000 i    a i    i  x000D  console log  Testing for Object with   Object keys a  length   keys   x000D  timeit isEmpty1 10000   x000D  timeit isEmpty2 10000   x000D  timeit isEmpty3 10000   x000D  timeit isEmpty4 10000   x000D   x000D   x000D

User · Answer

EDIT  Note that you should probably use ES5 solution instead of this since ES5 support is widespread these days  It still works for jQuery though     Easy and cross-browser way is by using jQuery isEmptyObject   if    isEmptyObject obj            do something     More  http   api jquery com jQuery isEmptyObject   You need jquery though

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Elegant way - use keys  var myEmptyObj       var myFullObj     key   value    console log Object keys myEmptyObj  length     0 console log Object keys myFullObj  length     1   https   developer mozilla org en-US docs Web JavaScript Reference Global Objects Object keys

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I m assuming that by empty you mean  has no properties of its own       Speed up calls to hasOwnProperty var hasOwnProperty   Object prototype hasOwnProperty   function isEmpty obj            null and undefined are  empty      if  obj    null  return true          Assume if it has a length property with a non-zero value        that that property is correct      if  obj length  gt  0     return false      if  obj length     0   return true          If it isn t an object at this point        it is empty  but it can t be anything  but  empty        Is it empty   Depends on your application      if  typeof obj      object   return true          Otherwise  does it have any properties of its own         Note that this doesn t handle        toString and valueOf enumeration bugs in IE  lt  9     for  var key in obj            if  hasOwnProperty call obj  key   return false             return true      Examples   isEmpty         true isEmpty 33      true  arguably could be a TypeError  isEmpty         true isEmpty         true isEmpty  length  0  custom property           true  isEmpty  Hello       false isEmpty  1 2 3       false isEmpty  test  1       false isEmpty  length  3  custom property   1 2 3       false   If you only need to handle ECMAScript5 browsers  you can use Object getOwnPropertyNames instead of the hasOwnProperty loop   if  Object getOwnPropertyNames obj  length  gt  0  return false    This will ensure that even if the object only has non-enumerable properties isEmpty will still give you the correct results

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Surprised to see so many weak answers on such a basic JS question    The top answer is no good too for these reasons    it generates a global variable returns true on undefined uses for   in which is extremely slow by itself function inside for   in is useless - return false without hasOwnProperty magic will work fine   In fact there s a simpler solution   function isEmpty value        return Boolean value  amp  amp  typeof value      object    amp  amp   Object keys value  length

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https   lodash com docs isEmpty comes in pretty handy     isEmpty          true   isEmpty          true   isEmpty null     true   isEmpty          true

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fast onliner for  dictionary -objects   function isEmptyDict d  for  var k in d  return false  return true

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var x     var y   x  hi   console log Object keys x  length   0  console log Object keys y  length   0   true false   http   jsfiddle net j7ona6hz 1

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For ECMAScript5  not supported in all browsers yet though   you can use   Object keys obj  length     0

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You can write a fallback if Array isArray and Object getOwnPropertyNames is not available  XX isEmpty   function a       if Array isArray a            return  a length  0             if  a           return true            if a instanceof Object            if a instanceof Date               return false                     if Object getOwnPropertyNames a  length    0               return true                      return false

User · Answer

No need for a library   function      must be within a function  var obj         the object to test   for var isNotEmpty in obj    will loop through once if there is a property of some sort  then     return alert  not empty    what ever you are trying to do once   return alert  empty      nope obj was empty do this instead

User · Answer

here s a good way to do it  function isEmpty obj      if  Array isArray obj         return obj length     0      else if  typeof obj      object         for  var i in obj          return false            return true      else       return  obj

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funtion isEmpty o i        for i in o                return 1           return 0

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here my solution  function isEmpty value        if Object prototype toString call value        object Array              return value length    0        else if value    null  amp  amp  typeof value      object             return Object getOwnPropertyNames value  length     0        else           return   value     value     0              Chears

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May be you can use this decision   var isEmpty   function obj      for  var key in obj      if obj hasOwnProperty key         return false    return true

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Underscore and lodash each have a convenient isEmpty   function  if you don t mind adding an extra library     isEmpty

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var hasOwnProperty   Object prototype hasOwnProperty  function isArray a        return Object prototype toString call a        object Array     function isObject a        return Object prototype toString call a        object Object     function isEmpty a        if  null    a          a return 0      if   number     typeof a     string     typeof a return 1      var b    0      if  isArray a             if   a length return 0          for  var c   0  c  lt  a length  c   isEmpty a c       b    1           return b           if  isObject a             for  var d in a hasOwnProperty call a  d   amp  amp   isEmpty a d       b    1            return b           return 0

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How bad is this   function obj       for var key in obj           return false     not empty            return true     empty

User · Answer

It might be a bit hacky  You can try this   if  JSON stringify data  length     2          Do something     Not sure if there is any disadvantage of this method

User · Answer

function isEmpty  o         for   var p in o              if   o hasOwnProperty  p       return false              return true

User · Answer

if  Object getOwnPropertyNames obj1  length  gt  0     alert  obj1 is empty

[javascript] Is object empty?

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