Beginning Ajax With ASP.NET (2006).pdf

JavaScript and the Document Object Model
Browser innovation continued at a rapid rate, and incompatibilities continued among different vendors’
browsers. Many libraries were developed that attempted to provide a common application program interface
(API) between the different browsers. These would typically enable a common way of developing
Dynamic HTML (DHTML) applications across many browsers, but they were only moderately successful.
During this time, Microsoft, Netscape, and a number of other companies worked with the World Wide
Web Consortium (W3C) to provide a consistent and standardized DOM. This was an attempt to remove
the current complexity with developing DHTML applications across a variety of browsers.
The W3C develops interoperable technologies (specifications, guidelines, software, and tools) for all
web-related technologies. You can visit their web site for more information at www.w3.org.
Throughout this chapter, you will look at the core components of JavaScript and methods of interacting
with and manipulating the DOM. While still not fully realized, cross-browser compatibility with respect
to the DOM is much improved and is much easier than it previously was. However, inconsistencies
among vendor implementations still remain, and there are still many libraries and frameworks available
to provide a common API across vendors’ browser implementations. Some of these libraries are discussed
in Chapter 9 of this book.
Today, JavaScript is the prevalent scripting language of browsers. It is the primary method of achieving
dynamic client-side interactivity in web applications. Microsoft has already initiated work at integrating
the powerful server-side programming environment of ASP.NET with JavaScript support. Technologies
such as asynchronous client scripting and Atlas will also be discussed in later chapters of this book.
All of these advanced technologies make use of the core components and features of JavaScript.
Digging into Some More JavaScript Basics
Chapter 2 started your introduction to JavaScript, particularly in showing how it can interact with the
browser environment to modify the HTML and CSS that make up a web page. In this chapter, you will
build on and extend what you learned in Chapter 2.
Take a look at the following simple JavaScript:
Basic Javascript
alert(“Hi, I am some simple JavaScript”);
Simple Javascript Page
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