Question

I can’t understand why window is under self and self is under window object.

if you go to dev-tools or Firebug and write window you got DOM window object that self is under this object. The weird part is that window is under self again!

You can write

window.self.window.self.window.self.window.self.window.self.window.self.window.self.window.self.window.self.window.self.window.self.window.self.window.self.window.self.window.self.window.self.window.self.window.self.window.self.window.self.window.self.window.self.window.self.window.self.window.self.window.self.window.self.window.self.window.self.window.self.window.self.window.self.window.self.window.self.window.self.window.self.window.self.window.self.window.self.window.self.window.self.window.self.window.self.window.self.window.self.window.self.window.self.window.self.window.self.window.self.window.self.window.self.window.self.window.self

and still you get window object!

How?!

Answer 1

In a response to one of my comments:

It is a circular reference, so it doesn’t end. The compiler only
creates one reference. It just happens to be a reference back to the
original object on which the reference was created. That’s why you can
do window.window.window… Like this: var obj = {}; obj.obj = obj;.
There’s only one reference created but it’s a reference back to the
original, so you can do obj.obj.obj.obj.obj.obj.obj === obj.

Comment can be seen here: Is window really global in Javascript?