HTML and CSS Reference
In-Depth Information
There is a lot to learn about JavaScript, but there are many free resources for JavaScript
code and JavaScript tutorials on the Web.
Here are a few sites that offer free tutorials or free scripts:
●
JavaScript Tutorials (
http://echoecho.com/javascript.htm)
●
JavaScript Tutorial for the Non-Programmer (
http://www.webteacher.com/
●
JavaScript Tutorials (
http://www.w3schools.com/JS)
As you visit these and other Web sites, be aware that it is unethical to copy and paste
JavaScript that another person has written. Many Web sites that offer free JavaScript
require that you link to them or place comments in the JavaScript to indicate the iden-
tity of the author. While it is unlikely that you would be sued for borrowing someone's
JavaScript, the right thing to do is to ask permission, and if given, honor requests for
links or identification.
Focus on Ethics
Once you are comfortable with XHTML, the JavaScript language is a good technology
to learn as you continue your studies. Try some of the resources listed and get your feet
wet. See Chapter 14 for a more detailed introduction to JavaScript. The next section
introduces Dynamic HTML, a technology that uses JavaScript.
Dynamic HTML is not a single technology; it is a group of technologies that work
together to change a Web page after it has been downloaded. These technologies
allow the Web page to respond to user actions. The following technologies are used:
Document Object Model, Cascading Style Sheets, and client-side scripting
(JavaScript).
●
Document Object Model (DOM).
The DOM defines every object and element on a
Web page. Its hierarchical structure can be used to access page elements and
apply styles to page elements. A portion of a basic DOM common to most
browsers is shown in Figure 11.17. A contributing factor to the complexity of
DHTML is the fact that not all Web browsers use the same DOM. There are
several different DOMs currently in use, including the W3C DOM, the Gecko
DOM (used by the Mozilla and Firefox browsers), and the WebKit DOM (used
by the Safari and Chrome browsers). It's good news for Web developers that
current versions of browsers such as Internet Explorer, Firefox, and Opera
support the W3C DOM (although it's common for browsers to support the W3C
DOM along with browser-specific enhancements).
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