javaScript Tutorial-- Introduction to the java Script
What is JavaScript?
JavaScript is a dynamic language that executes within a
browser. JavaScript code is embedded within an HTML page using the JavaScript
tag. The <script> tag is used to embed JavaScript code. JavaScript code can be embedded in:
An external file The header of the page The body of the page
In this example, JavaScript is embedded within the
header. As soon as the page is loaded
this code is executed.
|
<html>
<head>
<title>JavaScript Example</title>
<script
language="JavaScript 1.2"> <!-- document.write("Hello
World!"); //--> </script>
</head>
<body>The body</body>
</html>
|
The Document write method displays the text
Notice that the JavaScript code is enclosed in HTML comment
tags:
Client side Javascript
Client-side JavaScript is the most common form of the
language. The script should be included in or referenced by an HTML document
for the code to be interpreted by the browser. It means that a web page need
not be a static HTML, but can include programs that interact with the user,
control the browser, and dynamically create HTML content. The JavaScript
client-side mechanism provides many advantages over traditional CGI server-side
scripts. For example, you might use JavaScript to check if the user has entered
a valid e-mail address in a form field.
The JavaScript code is executed when the user submits the
form, and only if all the entries are valid, they would be submitted to the Web
Server.
JavaScript can be used to trap user-initiated events such as
button clicks, link navigation, and other actions that the user initiates
explicitly or implicitly.
Advantages of JavaScript
The merits of using JavaScript are:
·
Less server
interaction: You can validate user input before sending the page off to the
server. This saves server traffic, which means less load on your server.
·
Immediate feedback
to the visitors: They don't have to wait for a page reload to see if they have
forgotten to enter something.
·
Increased
interactivity: You can create interfaces that react when the user hovers over
them with a mouse or activates them via the keyboard.
·
Richer interfaces:
You can use JavaScript to include such items as drag-anddrop components and
sliders to give a Rich Interface to your site visitors.
Limitation of JavaScript
We cannot treat JavaScript as a full-fledged programming
language. It lacks the following important features:
·
Client-side
JavaScript does not allow the reading or writing of files. This has been kept
for security reason.
·
JavaScript cannot
be used for networking applications because there is no such support
available.
·
JavaScript doesn't have any multithreading or
multiprocessor capabilities.
Once again,
JavaScript is a lightweight, interpreted programming language that allows you
to build interactivity into otherwise static HTML pages.
JavaScript Development Tools
One of major
strengths of JavaScript is that it does not require expensive development
tools. You can start with a simple text editor such as Notepad. Since it is an
interpreted language inside the context of a web browser, you don't even need
to buy a compiler. To make our life simpler, various vendors have come up with
very nice JavaScript editing tools.
Some of them are
listed here:
·
Microsoft
FrontPage: Microsoft has developed a popular HTML
editor called FrontPage. FrontPage also provides web developers with a
number of JavaScript tools to assist in the creation of interactive websites.
·
Macromedia Dreamweaver MX: Macromedia Dreamweaver MX is a very popular HTML and JavaScript
editor in the professional web development crowd. It provides several
handy prebuilt JavaScript components, integrates well with databases, and
conforms to new standards such as XHTML and XML.
·
Macromedia HomeSite 5: HomeSite 5 is a well-liked HTML and JavaScript editor from
Macromedia that can be used to manage personal websites effectively.
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