As you know already, in JavaScript there's a global object provided by every host environment. In the browser environment, this is the window object. All global variables become properties of the window object.

>>> window.somevar = 1;

1

>>> somevar

1

Also, all of the core JavaScript functions (discussed in Chapter 2) are methods of the window object.

>>> parseInt('123a456')

123

>>> window.parseInt('123a456')

123

In addition to being the global object, the window object also serves a second purpose and that is to provide data about the browser environment. There's a window object for every frame, iframe, popup, or browser tab.

Let's see some of the browser-related properties of the window object. Again...