Session vii(java scriptbasics)

 JavaScript is a programming language designed for Web
pages that describes data and procedures in terms of
objects, methods, and properties, rather than variables,
routines, and statements.
 Unlike HTML, JavaScript is case sensitive. JavaScript is
plain text and when created in a text editor needs to be
saved as a text (ASCII) file.

 Newer editions of full featured WYSIWYG HTML editors
support some Java Scripting, and often enable coding in
their page source windows.
 If you begin doing JavaScript by cutting and pasting you
may often need to modify a few parts of the scripts, such
as names of objects. Many JavaScript's are available on
the WWW, and links to some popular JavaScript sites are
provided below.

 A team of Netscape and Sun Microsystems developers
originally created JavaScript.
 In 1998 the European Computer Manfacturers
Association (ECMA) announced the adoption of a
standard Internet scripting language based on JavaScript
1.1 that resolved the incompatibilities that existed in
scripting between various browser implementations.
Microsoft, Netscape,

 and other browser companies agreed to follow the
specification. The standard is called ECMAScript,
though the common name, JavaScript, has persisted.
The most recent version of JavaScript is 1.3 (ECMA-
262).

 Version 1.3 requires Netscape 4.06 or
 newer and Microsoft Internet Explorer (IE) 4.0 or newer.
 IE actually uses JScript, a modified version of JavaScript
that does not support all JavaScript commands.
 I therefore recommend testing your pages, and using a
Netscape browser when viewing Web pages with
JavaScripting.

 JavaScript can enhance the dynamics and interactive
features of Web pages by enabling calculations,
checking forms, writing interactive games, adding
special effects, customizing graphics selections, data
binding, and more. JavaScript is an interpreted
language that runs in the user's browser

 . JavaScript code works on any computer platform
with a JavaScript capable browser, such as
Navigator 2.0 or later,
 or Microsoft Internet Explorer 3.0 or later.
JavaScript capable browsers may allow disabling
JavaScript in their preferences. JavaScript is easier
to use than are programming languages.

 With JavaScript, developers do not need to compile
a program or work with a developer's kit. Also, the
many JavaScripts available on the Internet can
easily be modified and adapted to your own pages.

JavaScript programming uses specialized terminology.
◦ Dot Syntax
◦ Objects.
◦ Properties
◦ Methods
◦ Events
◦ Functions
◦ Variables
◦ Expressions
◦ Operators

 . Actions by page users trigger event handler
commands in the JavaScript. The program will
then perform whatever commands are assigned to
the event

 . Common event handlers are listed in the following table.
Event Handler Action
onAbort The user stopped loading a page
onBlur The user moves from an object
onChange The user changed an object
onClick The user mouse-clicked an object
onError An error occurred in the script

Event Handler Action
onMouseover The cursor has moved over the object
onMouseout The cursor has moved off the object
onSelect The user selected the object
onSubmit The user submitted a form
onUnload The user leaves the window
onFocus The user activates an object
onLoad The object has been loaded

 JavaScript scripts can be embedded in an HTML page or
can reside in a separate page.
 JavaScript is often placed in the <head> section of the
HTML document, but can also be placed in the <body>.
 JavaScript object attributes can also be placed in HTML
element tags. You can use JavaScript in an HTML
document in the following ways:

 As statements and functions within <script> and
</script> tags.
 By specifying a file as the JavaScript source using the
<src> attribute of the <script> element.
 By specifying a JavaScript expression as the value of an
HTML attribute and as event handlers within certain
other HTML tags.

 The first method places the JavaScript between the
<script> and </script> tags. When specifying a script
only the tags <script> and </script> are essential.
 It is recommendable to specify the script language as an
attribute of the script element. Browsers currently
assume JavaScript, but other programming languages
could become popular in the future.

 The standard to open scripting is <script
language="JavaScript">.
 The script language attribute can also specify the
version of JavaScript.
 It is also recommendable to specify the MIME type of
the script, to denote to the browser that the script is
plain text. This is accomplished with the attribute
type="text/javascript".

 The following example script redirects the browser to a page,
named javascript.html. The object is window, the variable property
is location, and the value equals the specified HTML file.
 <script language="javascript1.2" type="text/javascript">

</script>

 In the following examples I do not include the
<script>and </script> tags,
 HTML tags or comment lines. These examples are
employed using the methods described above.

 The first example is a method for displaying text in a
Web page.
 The syntax for this method can also be writeIn, a
method that attaches a break to each line of text.


 document.write("This is where you place the text
that will appear in the Web page.")
 The write method also permits use of HTML tags
within the parenthesis, as seen below.
 document.write("<b>Hello World.</b>")
 The writeIn method should be used with
preformatted text.

 var month = April;
var date = fifteenth;
 document.write("Remember, your taxes are due on
" + month + date);

Session vii(java scriptbasics)

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