Am i a function or a constructor?

@fetmataJul 22.2009

I was wondering if there is a way to determine from within a function body whether it is currently being used as a function, or used to construct a new object.

function Foo() {
/* Can I figure out here if I am currently constructing a new object, or just returning a value? */
}

var foo1 = new Foo();
var foo2 = Foo();

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JavaScript

@KorJul 22.2009 — #Check the function's [B]constructor[/B] property

<i>
 </i>function Foo(){
 if(this.constructor==Foo){alert('called with new')} [COLOR="SlateGray"]// creates an object[/COLOR]
 else{alert('called as function')} [COLOR="SlateGray"]// does not create an object[/COLOR]
 }

More about the [B]constructor [/B]property:

http://www.w3schools.com/jsref/jsref_constructor_array.asp

@fetmataauthorJul 22.2009 — #Thank you Kor. You are now my mentor ?

@KorJul 22.2009 — #Speaking about the [B]constructor[/B]... Interesting is that property is not readonly (at least not in all the cases). Strange enough, any kind of object, except for primitive such as Number, String and Boolean, can be modified:

<i>
 </i>function Foo(){}
 var myObj= new Foo(); // new created Object
 var myString= new String('blah');// new created String
 var myPrimiveString='blah'; // primitve String
 
 myObj.constructor=Array;
 myString.constructor=Array;
 myPrimitiveString.constructor=Array;
 
 alert([
 myObj.constructor===Array,
 myString.constructor===Array,
 myPrimitiveString.constructor===Array
 ])
 
 // alerts true,true,false

That's rather bad news for those who use serializer libraries or JSON parsers... Anyway, this is probably another topic ?

Am i a function or a constructor?

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