Javascript - get class owner of a function(method)

Question

Hi, there is a way to know what class own a function? Example:

function globalFunc(){
 //alert MyObject
}

function MyObject(){
}
MyObject.prototype.test=function(){
 globalFunc();
}

var o=new MyObject();
o.test();  //alert MyObject

Now im using this workaround:

function globalFunc(){
 alert(globalFunc.caller.__class__);
}

function MyObject(){
}
MyObject.prototype.test=function(){
 globalFunc();
}
MyObject.prototype.test.__class__=MyObject;

var o=new MyObject();
o.test();  //alert MyObject

But there is a big problem, look this:

function globalFunc(){
 alert(globalFunc.caller.__class__);
}

function MyObject(){
}
MyObject.prototype.test=function(){
 var temp=function(){
  globalFunc();
 }
 temp(); 
    /* to simulate a simple closure, this may be for example:
     element.addEventListener("click",temp,false);
    */
}
MyObject.prototype.test.__class__=MyObject;

var o=new MyObject();
o.test();  //alert undefined

So, there is a clear way to obtain this? I know where is the problem(class property is a property of only test and not temp), but i can't add class to temp too.

Thanks.

Answer 1

temp is the caller but it does not have the property __class__. You only defined that for test.

Answer 2

caller is non-standardised and really brittle; best avoided. Much better to pass the value explicitly:

MyObject.prototype.test= function() {
    element.addEventListener('click', function() {
        globalFunc(MyObject);
    });
};

or:

MyObject.prototype.test= function() {
    var myclass= arguments.callee.__class__;
    element.addEventListener('click', function() {
        globalFunc(myclass);
    });
};

Answer 3

You scenario is not entirely clear but here are some options:-

 function globalFunc()
 {
     alert(this.__class__);
     //Note globalFunc now has access to much more.
 }

 function MyObject(){ }
 MyObject.prototype.test=function(){
   globalFunc.call(this);
 }
 MyObject.prototype.__class__=MyObject;

To add a closure for event handling

MyObject.prototype.test = function(){
   var self = this;
   var elem = //get some element;
   //Not cross-browser but for illustration
   elem.addEventListener('click', fnEvent);
   function fnEvent() { globalFunc.call(self); }
   elem = null
}

Answer 4

In javascript there are no Classes. Instead several objects can "own" the same function. For example:

function myFun(){
  alert(this.name);
}

function Obj1(){
  this.name = "obj1";
}
Obj1.prototype.fun = myFun;

function Obj2(){
  this.name = "obj2";
}
Obj2.prototype.fun = myFun;
var obj1 = new Obj1();
var obj2 = new Obj2();
obj1.fun();
obj2.fun();

Answer 5

Functions are not "owned" in JavaScript. Functions are first class objects in JavaScript, which means they can be passed around like any other variable and assigned as properties of many objects.

this inside a function body will give you a reference to the object on which the function was called, if called as a method (e.g. myObj.myMethod()) or via the Function prototype's call() or apply() methods (e.g. myFunc.call(myObj)). Inside a function called on its own (e.g. myFunc()), this will usually be the global object (the same as window in most browsers).

Answer 6

Thanks for reply, some clarification.

Im trying to do a personal framwork OO oriented with private members.

So:

globalFunc is a special function, im using it to get "private" property and i can't call it with call method or passing some arguments, the only arguments im pass is "this":

Example, $() is global

Class({
    public:{
     MyClass:function(){
     },

     setName:function(name) {
      $(this).name=name; //set the private var name
     },
     getName:function(){
      return $(this).name;
     }
    },
    private:{
     name:"UNKNOWN"
    }
})

var o=new MyClass();
o.getName(); // UNKNOWN
o.setName("TEST!!!");
o.getName(); // TEST!!!
o.name; //undefined
$(o).name; //undefined

To works with inheritance, $(), i need to know what class call it and the object of the class.

All works good, but if i need to access a private members in a clousure i must add __class__ property to clouser!! And i not want this!

Thanks again and sorry for my bad english, im not native speaker.

Answer 7

I don't understand well what you are trying to do, but here's an idea that could inspire you something.
The "constructor" property helped me well when I was trying to use JS as a OO language.

o.constructor will give you the myObject function reference.

But in my opinion, you should give functional programming a try instead of OO to get the most from Javascript