What is the difference between this, self, window and window.self

Question

If I open an empty page and I run the following command in javascript console I obtain the same result:

  >>> this
  DOMWindow

  >>> self
  DOMWindow

  >>> window
  DOMWindow

  >>> window.self
  DOMWindow

What do they refer to? ...the same object or what else?

Answer 1

window is the reference to the current browser’s window the script executes in. window.self is obviously a self-reference of that within itself. And since self here is a property of the global object window, it can also be accessed as if it was a “global” variable itself: just self.

So the last three are under most circumstances indeed the same thing.

this however is completely different: it’s a variable pointing to the current scope. If you execute the following code in the console:

> var myPackage = {}
> myPackage.method = function() {console.log(this)}
> myPackage.method()

this will be pointing to the myPackage object (the scope of method).