Fundamentals of HTML Scripting

Fundamentals of HTML Scripting

The Dynamic HTML object model has evolved from the object models that were included in Microsoft Internet Explorer 3.0 and Netscape Navigator 3.0. This chapter provides a historical perspective, comparing the old object models with the one provided by Dynamic HTML and demonstrating the level of support provided by the different versions of the browsers.

Scripting languages have evolved alongside the HTML object models. By embedding scripts in your documents, you can access the HTML objects to manipulate the elements on your Web pages. This chapter introduces this powerful programming technique.

The following topics are covered in this chapter:

• Dynamic HTML object hierarchy The Dynamic HTML object hierarchy is the API for creating live and interactive pages. The objects in the hierarchy represent the browser and the elements of the HTML page. In this section, the object models supported by Internet Explorer 3.0 and Netscape Navigator 3.0 and 4.0 are discussed and compared to the Dynamic HTML object model supported by Internet Explorer 4.0.

• Authoring scripts The Dynamic HTML object model is accessed by writing scripts and associating them with the HTML document. A script is associated with the HTML document by using a Script element, which contains executable code in a specified language. The Script element can also be used to associate external script libraries with the document.

• Choosing a scripting language: JavaScript vs. VBScript The two primary programming languages used on the Web are JavaScript and VBScript. Both languages can fully manipulate the Dynamic HTML objects. This section helps you determine which language to use for specific circumstances.

• Advanced JavaScript techniques This section discusses some of the JavaScript techniques used throughout this book. It is not meant to provide a language tutorial, but rather to familiarize you with some of the interesting features of the JavaScript language and their relationship to Dynamic HTML.

• Scripting and Web security Security is a widespread concern on the Web. A programming language imposes limitations in order to ensure the clients' security, and a programmer must understand these limitations. This section introduces the security model for Dynamic HTML. Additional security issues are addressed throughout this book.

NOTE: This chapter uses elements of the Dynamic HTML object model to demonstrate various techniques. For each such use, you will find a reference to the chapter in which the feature is discussed in detail.

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