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VBScript
As the previous section noted, JavaScript is based on concepts drawn from C, C++, and Perl. At the same time, a significant number of business application developers have little experience with these languages, focusing instead on Visual Basic. To promote the development of Web-enabled business applications using Microsoft technologies, Microsoft introduced VBScript, a scripting language that is a subset of Visual Basic.
VBScript is a natural choice for application developers currently using Visual Basic or Visual Basic for Applications (VBA). The downside is that only Internet Explorer natively supports VBScript, although there is a plug-in (see the sidebar entitled "Plug-in Technology") for VBScript in Netscape Navigator.
The major difference between JavaScript and VBScript is syntax. Although neither language supports inheritance, JavaScript is more strongly object-oriented than is VBScript. With JavaScript, developers can define and implement classes.
Some developers feel that JavaScript suffers from its relatively small set of built-in functionality. For many scripting tasks that require custom development, VBScript provides a richer set of built-in tools. Examples include dialog boxes, interaction with ActiveX controls, and date functions.
Plug-in Technology
Plug-ins are software components that are used to dynamically extend the document content types that a Web browser understands. For example, there are plug-ins that allow the user to load audio, video, word processor and spreadsheet documents, and even new scripting engines into the browser.
A plug-in is associated with one or more MIME types. When the browser encounters an embedded type in a Web page that requires a plug-in, it checks for a matching plug-in, instantiates it, and passes the media reference to the plug-in. The plug-in is then responsible for the appropriate processing of the media.