What is the difference between a window and a window?

Question

What is a Window ?

Here is what I see on the console in Chrome:

  window Window {top: Window, window: Window, location: Location, external: Object, chrome: Object…} Window function Window() { [native code] } 

Answer 1

Window is a function, as you can see. This is a constructor for windows (but you cannot create new windows directly using the constructor, you usually use the Window.open function). Window.prototype thus contains methods that you can call in the window).

Window - a global variable containing an instance of Window is a browser window containing your document (in fact, this is not a "window", but a tab in modern browsers).

You can check that

 window instanceof Window 

is an

 true 

Answer 2

Window is a constructor function that is used to create a Window .

To see this, try alert(window.constructor === Window) .