How to check if object has any properties in JavaScript

Question

Assuming I declare   var ad          How can I check whether this object will contain any user-defined properties

User · Answer

Very late answer  but this is how you could handle it with prototypes   Array prototype Any   function func        return this some func    function x    return x        Object prototype IsAny   function         return Object keys this  Any

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for var memberName in ad        Member Name  memberName     Member Value  ad memberName      Member means Member property  member variable  whatever you want to call it      The above code will return EVERYTHING  including toString    If you only want to see if the object s prototype has been extended   var dummyObj         for var memberName in ad      if typeof dummyObj memberName      typeof ad memberName    continue    note A     Member Name  memberName     Member Value  ad memberName       Note A  We check to see if the dummy object s member has the same type as our testing object s member   If it is an extend  dummyobject s member type should be  undefined

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Late answer  but some frameworks handle objects as enumerables  Therefore  bob js can do it like this   var objToTest       var propertyCount   bob collections extend objToTest  count

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Most recent browsers  and node js  support Object keys   which returns an array with all the keys in your object literal so you could do the following   var ad        Object keys ad  length   this will be 0 in this case   Browser Support  Firefox 4  Chrome 5  Internet Explorer 9  Opera 12  Safari 5  https   developer mozilla org en-US docs Web JavaScript Reference Global Objects Object keys

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What about making a simple function   function isEmptyObject obj      for var prop in obj        if  Object prototype hasOwnProperty call obj  prop           return false              return true     isEmptyObject         true isEmptyObject  foo  bar         false   The hasOwnProperty method call directly on the Object prototype is only to add little more safety  imagine the following using a normal obj hasOwnProperty      call   isEmptyObject  hasOwnProperty  boom         false     Note   for the future   The above method relies on the for   in statement  and this statement iterates only over enumerable properties  in the currently most widely implemented ECMAScript Standard  3rd edition  the programmer doesn t have any way to create non-enumerable properties   However this has changed now with ECMAScript 5th Edition  and we are able to create non-enumerable  non-writable or non-deletable properties  so the above method can fail  e g    var obj       Object defineProperty obj   test     value   testVal      enumerable  false    writable  true    configurable  true     isEmptyObject obj      true  wrong   obj hasOwnProperty  test       true  the property exist     An ECMAScript 5 solution to this problem would be   function isEmptyObject obj      return Object getOwnPropertyNames obj  length     0      The Object getOwnPropertyNames method returns an Array containing the names of all the own properties of an object  enumerable or not  this method is being implemented now by browser vendors  it s already on the Chrome 5 Beta and the latest WebKit Nightly Builds   Object defineProperty is also available on those browsers and latest Firefox 3 7 Alpha releases

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With jQuery you can use     isEmptyObject obj      Returns  Boolean   As of jQuery 1 4 this method checks both properties on the object itself and properties inherited from prototypes  in that it doesn t use hasOwnProperty    With ECMAScript 5th Edition in modern browsers  IE9   FF4   Chrome5   Opera12   Safari5   you can use the built in Object keys method   var obj     blah  1    var isEmpty    Object keys obj  length    Or plain old JavaScript   var isEmpty   function obj                   for var p in obj                     return false                                  return true

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You can loop over the properties of your object as follows  for var prop in ad        if  ad hasOwnProperty prop                handle prop as required          It is important to use the hasOwnProperty   method  to determine whether the object has the specified property as a direct property  and not inherited from the object s prototype chain  Edit From the comments  You can put that code in a function  and make it return false as soon as it reaches the part where there is the comment

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var hasAnyProps   false  for  var key in obj    hasAnyProps   true  break       as of this line hasAnyProps will show Boolean whether or not any iterable props exist   Simple  works in every browser  and even though it s technically a loop for all keys on the object it does NOT loop through them all   either there s 0 and the loop doesn t run or there is some and it breaks after the first one  because all we re checking is if there s ANY   so why continue

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You can use the following   Double bang    property lookup  var a            true var a     null     false   hasOwnProperty This is something that I used to use   var myObject       name   John     address  null    if  myObject hasOwnProperty  address         true      do something if it exists      However  JavaScript decided not to protect the method   s name  so it could be tampered with    var myObject       hasOwnProperty   I will populate it myself        prop in myObject  var myObject       name   John     address  null    developer  false     developer  in myObject     true  remember it s looking for exists  not value    typeof  if  typeof myObject name      undefined          do something     However  it doesn t check for null   I think this is the best way   in operator   var myObject       name   John     address  null     if  name  in myObject      console log  Name exists in myObject     else    console log  Name does not exist in myObject        result       Name exists in myObject   Here is a link that goes into more detail on the in operator  Determining if an object property exists

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If you re using underscore js then you can use the   isEmpty function   var obj       var emptyObject     isEmpty obj

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ES6 function         Returns true if an object is empty      param      obj the object to test     return  boolean  returns true if object is empty  otherwise returns false     const pureObjectIsEmpty   obj   gt  obj  amp  amp  obj constructor     Object  amp  amp  Object keys obj  length     0    Examples    let obj    this is an object with String constructor  console log pureObjectIsEmpty obj      empty  true  obj      console log pureObjectIsEmpty obj      empty  true  obj      console log pureObjectIsEmpty obj      empty  true  obj     prop  value    console log pureObjectIsEmpty obj      empty  true  obj    prop  value   console log pureObjectIsEmpty obj      empty  false

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How about this   var obj       var isEmpty    obj  var hasContent     obj

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When sure that the object is a user-defined one  the easiest way to determine if UDO is empty  would be the following code   isEmpty    b b Troy III p a e   function x p  for p in x return 1 return 0     Even though this method is  by nature  a deductive one  - it s the quickest  and fastest  possible    a     isEmpty a   gt  gt  true  a b 1 isEmpty a   gt  gt  false    p s    don t use it on browser-defined objects

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You can use the built in Object keys method to get a list of keys on an object and test its length  var x          some code where value of x changes and than you want to check whether it is null or some object with values  if Object keys x  length       Your code here if x has some properties

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for  var hasProperties in ad  break  if  hasProperties             ad has properties   If you have to be safe and check for Object prototypes  these are added by certain libraries and not there by default    var hasProperties   false  for  var x in ad        if  ad hasOwnProperty x             hasProperties   true          break          if  hasProperties             ad has properties

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If you are willing to use lodash  you can use the some method     some obj     returns true or false   See this small jsbin example

[javascript] How to check if object has any properties in JavaScript?

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