programmers of all skill levels control the behavior of software
objects. The language is used most widely today in Web browsers whose
software objects tend to represent a variety of HTML elements in a
document and the document itself. But the language can be--and is--used
with other kinds of objects in other environments. For example, Adobe
glue together objects that are unique to the forms generated by Adobe
language, from the objects it can communicate with in any particular
environment. When used for Web documents, the scripts go directly inside
the HTML documents and are downloaded to the browser with the rest of
the HTML tags and content.
client-side scripting and programming language developed by Netscape
Communications Corp. and Sun Microsystems.
at Sun Microsystems. While the two languages share some common syntax,
they were developed independently of each other and for different
audiences. Java is a full-fledged programming language tailored for
network computing; it includes hundreds of its own objects, including
objects for creating user interfaces that appear in Java applets (in Web
relies on whatever environment it's operating in for the user interface,
such as a Web document's form elements.
under development. A licensing deal between Netscape and Sun at the last
minute let Netscape plug the "Java" name into the name of its scripting
language. Programmers use entirely different tools for Java and
be ignorant of the other. The two languages don't rely on each other and
are intended for different purposes. In some ways, the "Java" name on
than Java and can offer a gentle introduction for newcomers who want to
graduate to Java and the kinds of applications you can develop with it.
is ECMAScript revision 3.
(0 refers to the index of the form – if you have more than one form in a
page, then the first one has the index 0, second has index 1 and so on).
You can directly add a script element inside the body of page.
1. For example, to add the "last updated line" to your pages, In your
page text, add the following:
<p>blah, blah, blah, blah, blah.</p>
<!-- Hiding from old browsers
document.write("Last Updated:" +
<p>yada, yada, yada.</p>
(Note: the first comment, "<--" hides the content of the script from
doesn't try to interpret the "-->". If your audience has much older
of your audience has newer browsers, the comments can be omitted. For
brevity, in most examples here the comments are not shown. )
Functions and global variables typically reside inside the <head>
<title>Default Test Page</title>
var myVar = "";
referenced from an HTML page. (Don't use the shorthand ending "<script
... />). These are typically placed in the <head> element.
I/O operations like reading or writing a file is not possible with
applet that reads files for the script.
How to detect the operating system on the client machine?
In order to detect the operating system on the client machine, the
string (property) should be used.
make the page more immediately interactive, that is, interactive without
having to submit every little thing to the server for a server program
to re-render the page and send it back to the client. For example,
consider a top-level navigation panel that has, say, six primary image
map links into subsections of the Web site. With only a little bit of
scripting, each map area can be instructed to pop up a more detailed
list of links to the contents within a subsection whenever the user
rolls the cursor atop a map area. With the help of that popup list of
links, the user with a scriptable browser can bypass one intermediate
menu page. The user without a scriptable browser (or who has disabled
time-consuming path to the desired content.