BOM

The BOM is a collection of objects that give you access to the browser and the computer screen. These objects are accessible through the global object window.

The window object revisited

As you already know, in JavaScript, there's a global object provided by the host environment. In the browser environment, this global object is accessible using window. All global variables are also accessible as properties of the window object. For example, take a look at the following code:

    > window.somevar = 1; 
           1 
    > somevar; 
           1 

Additionally, all the core JavaScript functions, discussed in Chapter 2, Primitive Data Types, Arrays, Loops, and Conditions, are methods of the global object. Consider the following piece of code:

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

In addition to being a reference to the global object, the window object also serves a second purpose-providing...