Java script202

JavaScript

By
Dr. Ejaz Ahmed

Scripting Language Javascript
• JavaScript was designed to add interactivity to HTML
pages
• JavaScript is a scripting language
• A scripting language is a lightweight programming
language
• JavaScript is usually embedded directly into HTML
pages
• JavaScript is an interpreted language (means that
scripts execute without preliminary compilation)
• Everyone can use JavaScript without purchasing a
license

Are Java and JavaScript the same?
• NO!
• Java and JavaScript are two completely different
languages in both concept and design!
• Java (developed by Sun Microsystems) is a
powerful and much more complex programming
language - in the same category as C and C++.
• JavaScript was invented by Brendan Eich at
Netscape (with Navigator 2.0), and has appeared
in all browsers since 1996.

Introduction
• JavaScript was designed to add interactivity to HTML pages.
• JavaScript is a scripting language.
• JavaScript is usually embedded directly into HTML pages.
• JavaScript is an interpreted language (means that scripts
execute without preliminary compilation).
• It is an event-driven language.
• To insert a JavaScript into an HTML page, use the <script>
tag.
• Inside the <script> tag use the type attribute to define the
scripting language.
• The <script> and </script> tells where the JavaScript starts
and ends. <script type="text/javascript">

How to use javascript?
• The common way to use the javascript is as follows;
• Define some HTML tag with ID attribute value given.
• In that HTML tag add/call the function statement and
bind it to some event on which you want to invoke the
javascript function (event handler).
• Write the said function (event handler) between
<script> and </script> tags.
• When the page downloads, your handler will be called
on event you described within the HTML tag.

What can a JavaScript do?
• JavaScript gives HTML designers a programming tool - HTML authors
are normally not programmers, but JavaScript is a scripting language
with a very simple syntax! Almost anyone can put small "snippets" of
code into their HTML pages
• JavaScript can put dynamic text into an HTML page - A JavaScript
statement like this:
document.write("<h1>" + name + "</h1>")
• can write a variable text into an HTML page
• JavaScript can react to events - A JavaScript can be set to execute
when something happens, like when a page has finished loading or
when a user clicks on an HTML element
• JavaScript can read and write HTML elements - A JavaScript can read
and change the content of an HTML element
• JavaScript can be used to validate data - A JavaScript can be used to
validate form data before it is submitted to a server. This saves the
server from extra processing

Ajax
• AJAX = Asynchronous JavaScript and XML.
• AJAX is not a new programming language, but a new way to
use existing standards.
• AJAX is the art of exchanging data with a server, and update
parts of a web page - without reloading the whole page.
• AJAX allows web pages to be updated asynchronously by
exchanging small amounts of data with the server behind the
scenes. This means that it is possible to update parts of a
web page, without reloading the whole page.
• Classic web pages, (which do not use AJAX) must reload the
entire page if the content should change.
• Examples of applications using AJAX: Google Maps, Gmail,
Youtube, and Facebook tabs.

Web Servers
• jakarta-tomcat-5.0.28 (with jdk)
• Dot Net (.Net) Framwork
• IBM WebSphere
• ZendCore
• etc.

Getting Started with JavaScript
Event: onclick

Introducing document
‘getElementById()’ method

Example – Data conversions and
Calculations

Example – Dialogue Box & Pop up
Window

Code - Dialogue Box & Pop up
Window

Example – Dialogue Box &
Calculations

Pop up window and Document
Write

Java script202

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