DOM:window.window

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« Gecko DOM Reference

[edit] Summary

The window property of a window object points to the window object itself. Thus the following expressions all return the same window object:

window.window
window.window.window
window.window.window.window
  ...

In web pages, the window object is also a global object. This means that:

1. global variables of your script are in fact properties of window:

   var global = {data: 0};
   alert(global === window.global); // displays "true"
   

2. you can access built-in properties of the window object without having to type window. prefix:

   setTimeout("alert('Hi!')", 50); // equivalent to using window.setTimeout.
   alert(window === window.window); // displays "true"
   

The point of having the window property refer to the object itself was (probably) to make it easy to refer to the global object (otherwise you'd have to do a manual var window = this; assignment at the top of your script).

Another reason is that without this property you wouldn't be able to write, for example, "window.open('http://google.com/')" - you'd have to just use "open('http://google.com/')" instead.

[edit] Specification

DOM Level 0. Not part of any standard.