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home >> chapters >> chapter 9 (second edition)
Chapter 9 – JavaScript Object Models
An object model defines the interface to the various aspects of the browser and the
document that can be manipulated by JavaScript. In JavaScript, there are a variety of object models based upon browser type and version, but in general we see two
primary object models employed—a Browser Object Model and a Document Object Model
(DOM). The Browser Object Model provides access to the various characteristics of a browser
such as the browser window itself, the screen characteristics, the browser history, and so on. The DOM, on the other hand, provides access to the contents of the browser window, namely the document including the various (X)HTML elements, CSS properties, and any text items.
While it would seem clear, the unfortunate reality is that the division between the DOM and
the Browser Object Model is at times somewhat fuzzy and the exact document manipulation
capabilities of a particular browser's implementation of JavaScript vary significantly. This
section starts our exploration of the use of the various aspects of JavaScript object models that are fundamental to the proper use of the language.We begin this chapter with an exploration
of JavaScript's initial object model and then examine the various additions made to the object
model by browser vendors. This apparent history lesson will uncover the significant problems
with the "DHTML" object models introduced by the browser vendors and still used by many
of today's JavaScript programmers and will motivate the rise of the standard DOM model
promoted by the W3C, which is covered in the following chapter.
 Download Chapter 9 (Second Edition) [ PDF - 360KB ]
The first edition version of this chapter is archived here for your convenience [ PDF - 1.0MB ].
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