In Javascript, let\'s say we have a main page (main.html) which contains an (iframe.html)
Now inside this ifr
The concept of window is tied to the document: There's one window per document, and one document per window.
That means elements, which have their own document, also have their own window, just like a pop-up window or the main navigator window.
So, you'll indeed have to use window.parent to access the container of an element, just like you have to use window.opener to access the owner of a pop-up window.
EDIT: Both window.parent and parent.window are valid expressions that return the same object. That's because the window object is the default context in scripting (unqualified names are parsed as members of window), and window objects have a window property that refers to themselves.
So, parent.window is evaluated as window.parent.window, which is the same object as window.parent.
That said, I do prefer using window.parent, to avoid the (minimal) overhead associated with the extra property access.