HTML, XHTML & CSS

20
Part IV: Scripting and (X)HTML
An innovative use of JavaScript occurs in Gmail, the free Web-based e-mail
service from Google, which you can find at www.gmail.com. Gmail uses
JavaScript to load an entire e-mail user interface into the user’s browser,
which makes Gmail much more responsive to user actions than most other
Web-based mail programs. Gmail uses JavaScript to keep to an absolute minimum
the number of times the page has to fetch additional information from
the servers. By doing much of the processing in the user’s browser, the Gmail
Web application feels more like an e-mail program that runs on your computer.
Figure 13-5 shows the JavaScript-powered Gmail interface. It’s a great
example of the power of JavaScript.
Figure 13-5: The Gmail interface is powered by JavaScript.
JavaScript is a scripting language that runs
inside the browser, but there are other scripting
languages that run on the server side, such
as Perl, ASP (Active Server Pages), PHP (PHP
Hypertext Preprocessor, an (X)HTML embedded
scripting language), Python, .NET, and others.
Programs written in these languages reside
on the server and are called by the Web page,
usually in response to a form filled out by the
user. People who write these Web pages may
include snippets of code that pass bits of information
from the HTML page to the program on
Server-side scripting
the server. When called, the program runs and
then returns a result of some sort to the user.
Amazon (www.amazon.com) runs a familiar
e-commerce Web application that runs mostly
on the server side, using server scripts. Web
pages displayed by the browser when you visit
Amazon result from processing server-side
scripts, all of which take place before the page
ever hits your browser. If you’d like more information
on JavaScript and what it can do for
you, check out JavaScript For Dummies, Quick
Reference by Emily A. Vander Veer.