How to get class object s name as a string in Javascript

Question

Let s say I instantiate an object in Javascript like this  var myObj   new someObject     Now  is it possible to obtain the var object s name as string  myObj  from within one of the class methods   Additional details  edited   The reason why I would like to get the name of the variable holding reference to the object is that my new myObj would create a new clickable DIV on the page that would need to call a function myObj someFunction    As I insert the new DIV I need to know the name of the variable holding reference to the object  Is there maybe a better way of doing this   You are right  sorry for the mixup in terminology  The reason why I would like to get the name of the variable holding reference to the object is that my new myObj would create a new clickable DIV on the page that would need to call a function myObj someFunction    As I insert the new DIV I need to know the name of the variable holding reference to the object  Is there maybe a better way of doing this

User · Answer

You might be able to achieve your goal by using it in a function  and then examining the function s source with toString     var whatsMyName        Just do something with the whatsMyName variable  no matter what function func    var v   whatsMyName       Now that we re using whatsMyName in a function  we could get the source code of the function as a string  var source   func toString        Then extract the variable name from the function source  var result    var v             exec source    alert result 1       Should alert  whatsMyName

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You can do it converting by the constructor to a string using  toString      function getObjectClass obj      if  typeof obj     object     obj     null  return false     else return    w      exec obj constructor toString    1

User · Answer

Shog9 is right that this doesn t make all that much sense to ask  since an object could be referred to by multiple variables  If you don t really care about that  and all you want is to find the name of one of the global variables that refers to that object  you could do the following hack   function myClass        this myName   function              search through the global object for a name that resolves to this object     for  var name in this global         if  this global name     this           return name            store the global object  which can be referred to as this at the top level  in a    property on our prototype  so we can refer to it in our object s methods myClass prototype global   this    create a global variable referring to an object var myVar   new myClass   myVar myName      returns  myVar    Note that this is an ugly hack  and should not be used in production code  If there is more than one variable referring to an object  you can t tell which one you ll get  It will only search the global variables  so it won t work if a variable is local to a function  In general  if you need to name something  you should pass the name in to the constructor when you create it   edit  To respond to your clarification  if you need to be able to refer to something from an event handler  you shouldn t be referring to it by name  but instead add a function that refers to the object directly  Here s a quick example that I whipped up that shows something similar  I think  to what you re trying to do   function myConstructor        this count   0   this clickme   function          this count    1     alert this count         var newDiv   document createElement  div     var contents   document createTextNode  Click me          This is the crucial part  We don t construct an onclick handler by creating a      string  but instead we pass in a function that does what we want  In order to      refer to the object  we can t use this directly  since that will refer to the       div when running event handler   but we create an anonymous function with an       argument and pass this in as that argument    newDiv onclick    function  obj         return function            obj clickme              this     newDiv appendChild contents    document getElementById  frobnozzle   appendChild newDiv     window onload   function        var myVar   new myConstructor

User · Answer

Immediately after the object is instantiatd  you can attach a property  say name  to the object and assign the string value you expect to it   var myObj   new someClass    myObj name  myObj    document write myObj name     Alternatively  the assignment can be made inside the codes of the class  i e   var someClass   function P    this name P       rest of the class definition        var myObj   new someClass  myObj    document write myObj name

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Short answer  No  myObj isn t the name of the object  it s the name of a variable holding a reference to the object - you could have any number of other variables holding a reference to the same object  Now  if it s your program  then you make the rules  if you want to say that any given object will only be referenced by one variable  ever  and diligently enforce that in your code  then just set a property on the object with the name of the variable  That said  i doubt what you re asking for is actually what you really want  Maybe describe your problem in a bit more detail      Pedantry  JavaScript doesn t have classes  someObject is a constructor function  Given a reference to an object  you can obtain a reference to the function that created it using the constructor property   In response to the additional details you ve provided  The answer you re looking for can be found here  JavaScript Callback Scope  and in response to numerous other questions on SO - it s a common point of confusion for those new to JS   You just need to wrap the call to the object member in a closure that preserves access to the context object

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As a more elementary situation it would be nice IF this had a property that could reference it s referring variable  heads or tails  but unfortunately it only references the instantiation of the new coinSide object   javascript      it would be nice but     a solution NOT     function coinSide   this ref this      can  ref be set so as to identify it s referring variable   heads or tails     heads   new coinSide    tails   new coinSide    toss   Math random   lt 0 5   heads   tails  alert toss ref   alert   FF s Gecko engine shows  n ntoss toSource    is     toss toSource       which always displays    object Object     and Firefox s Gecko engine shows    toss toSource    is    1  ref  1      Of course  in this example  to resolve  1  and hence toss  it s simple enough to test toss  heads and toss  tails  This question  which is really asking if javascript has a call-by-name mechanism  motivates consideration of the counterpart  is there a call-by-value mechanism to determine the ACTUAL value of a variable  The example demonstrates that the  values  of both heads and tails are identical  yet alert heads  tails  is false   The self-reference can be coerced as follows   avoiding the object space hunt and possible ambiguities as noted in the How to get class object  39 s name as a string in Javascript  solution   javascript  function assign n v   eval  n       v    eval  n    ref     n          function coinSide      assign  heads    new coinSide      assign  tails    new coinSide      toss   Math random   lt 0 5   heads   tails  alert toss ref     to display heads or tails   It is perhaps an anathema to the essence of Javascript s language design  as an interpreted prototyping functional language  to have such capabilities as primitives   A final consideration    javascript       item new Object    refName  item   deferAgain  refName        alert  deferAgain eval deferAgain  eval eval deferAgain    join   n       so  as stipulated      javascript    function bindDIV objName        return eval  objName    new someObject    objName               function someObject objName       this div   n lt DIV onclick  window opener         window opener - hiccup                     objName                 someFunction    gt clickable DIV lt  DIV gt  n       this someFunction function   alert   my variable object name is   objName           with window open     test   document                  see above hiccup           write   lt html gt          bindDIV  DIVobj1   div        bindDIV  DIV2   div         alias bindDIV  multiply    div         an aliased DIV clone  multiply div          lt  html gt         close           void  0        Is there a better way          better  as in easier  Easier to program  Easier to understand  Easier as in faster execution  Or is it as in      and now for something completely different

User · Answer

If you don t want to use a function constructor like in Brian s answer you can use Object create   instead -  var myVar     count  0    myVar init   function n        this count   n     this newDiv      myVar newDiv   function         var newDiv   document createElement  div       var contents   document createTextNode  Click me        var func   myVar func this      newDiv addEventListener            newDiv addEventListener  click   func  false             newDiv attachEvent  onclick   func      newDiv appendChild contents      document getElementsByTagName  body   0  appendChild newDiv     myVar func   function  thys       return function           thys clickme            myVar clickme   function         this count    1    alert this count     myVar init 2   var myVar1   Object create myVar  myVar1 init 55    var myVar2   Object create myVar  myVar2 init 150       etc   Strangely  I couldn t get the above to work using newDiv onClick  but it works with newDiv addEventListener   newDiv attachEvent   Since Object create is newish  include the following code from Douglas Crockford for older browsers  including IE8   if  typeof Object create      function         Object create   function  o            function F              F prototype   o         return new F

User · Answer

This is pretty old  but I ran across this question via Google  so perhaps this solution might be useful to others   function GetObjectName myObject       var objectName JSON stringify myObject  match            1       return objectName      It just uses the browser s JSON parser and regex without cluttering up the DOM or your object too much

User · Answer

Some time ago  I used this     Perhaps you could try    function        var my var   function get this name            alert  I     this init                my var prototype init   function            return my var name            new my var           Pop an Alert   I get this name

[javascript] How to get class object's name as a string in Javascript?

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