The Book of JavaScript, 2nd Edition

Using the Right Name: How Windows See Themselves and Each Other

Every window is a bit egocentric and thinks of itself as window. Let's say you open a web page titled The Original Window. Now let's say that window opens a second window, new_window.html (titled The New Window), using JavaScript, like this:

var new_window =
    window.open("new_window.html","new_window","height=100,width=100");

These two windows see each other in different ways. The original window thinks the new window is called new_window. The new window, however, thinks of itself as window. This means if you want to close the new window using JavaScript inside the original window, you'd write this code:

new_window.close();

But to close the new window using JavaScript inside the new window, ...