The window object represents a window containing a DOM document; the document property points to the DOM document loaded in that window. A window for a given document can be obtained using the document.defaultView property.
The Window.sizeToContent() method sizes the window according to its content. In order for it to work, the DOM content should be loaded when this function is called, for example once the DOMContentLoaded event has been thrown.
The WindowEventHandlers.onbeforeunload event handler property contains the code executed when the beforeunload is sent. This event fires when a window is about to unload its resources. The document is still visible and the event is still cancelable.