Chapter 18: JavaScript and Embedded Objects

Overview

Modern browsers support many technologies beyond (X)HTML, CSS, and JavaScript. A wide variety of extra functionality is available in the form of browser plug-ins, ActiveX controls, and Java applets. These technologies provide extended capabilities that can make Web pages appear more like applications than marked -up text. Embedded objects provide a natural complement to the limited capabilities of scripting languages like JavaScript.

Embedded objects come in many forms, but the most popular are multimedia in nature. A good example is Macromedia Flash files, which allow designers to add advanced vector graphics and animation to Web sites. Various other types of embedded video, sound, and live audio are also quite popular. Embedded Java applets are often included in pages that require more advanced graphics, network, or processing functionality.

Browsers provide the bridge that facilitates communication between JavaScript and embedded objects. The way this communication is carried out is essentially non-standardized, although browser vendors adhere to their own ad hoc standards, which are in widespread use. Even so, there are numerous concerns when dealing with embedded objects. First, including them makes the assumption that the user s browser has the capability to handle such objects. Second, even if the user does have an appropriate extension installed, many users find embedded objects annoying because they increase download time while only occasionally improving the overall utility of the site. Third, users with older browsers and users on non-Windows platforms are often unable to use embedded objects because of lack of support.

This chapter introduces the way that JavaScript can be used to interact with embedded objects in most major browsers. Complex integration of objects with JavaScript requires more comprehensive information, which can be found at browser and plug-in vendor sites.