By Tharith Sriv

To write a web page you use: HTML (HyperText Markup Language), ASP (Active Server Page), PHP (HyperText Preprocessor), JavaScript, Java, etc.

JavaScript? JavaScript is the most popular scripting

language on the internet, and works in all major browsers, such as Internet Explorer, Firefox, Chrome, Opera, and Safari.

What should I know before learning JavaScript? Before you continue you should have a

basic understanding of the following: HTML / XHTML

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

JavaScript? A scripting language used for Web page

design. Enables you to enhance static web

applications How?

by providing dynamic, personalized, and interactive content.

First appeared in 1995, its main purpose was to handle some of the input validation that had previously been left to server-side languages such as Perl.

JavaScript is not the only scripting language; there are others such as VBScript and Perl.

So, why JavaScript? Because of its widespread use and

availability: Many browsers support JavaScript. VBScript is used for the same purposes as

JavaScript. But, supported by very limited number of Web browsers (especially IE).

The answer is 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 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

JavaScript can be used to detect the visitor's browser - A JavaScript can be used to detect the visitor's browser, and - depending on the browser - load another page specifically designed for that browser

JavaScript can be used to create cookies - A JavaScript can be used to store and retrieve information on the visitor's computer

A simple text editor. Notepad is possible. EditPlus is recommended. How?

EditPlus is an advanced text editor

You can also use another Advanced Text Editor, those providing line numbering, search and replace tools, and so on. For example, Adobe Dreamweaver, …

With scripts in previous slide, Mozilla Firefox displays the following:

Not all old Web browsers support JavaScript.

However, most of new Web browsers can support it.

Here are Versions of JavaScript which are supported by different Web browsers.

In order to run client-side JavaScript, you must embed the code in the HTML document.

There are several different ways to embed JavaScript scripts in HTML:a. As statements and functions using the

<SCRIPT> tagb. As event handlers using HTML tag attributesc. As short statements resembling URLs

The <SCRIPT> TagInternal Scripts

The <SCRIPT> tag is used to enclose JavaScript code in HTML documents.

Here is the general syntax:

<SCRIPT LANGUAGE="JavaScript">

[JavaScript statements...]</SCRIPT>

The <SCRIPT LANGUAGE="JavaScript"> tag acts like all other HTML tags.

Notice that it must be followed by its closing counterpart, </SCRIPT>.

Every statement you put between the two tags is interpreted as JavaScript code.

1. In the same file as HTML.2. Use an external js-file.

A way to do this is to write JavaScript codes and save it as a js-file (for example, myscript.js).

In your HTML file at where you want to write your JavaScript codes, just put something like:

<script language=JavaScript src=“abc.js”>[additional javascript statements]

</script>

Remember, JavaScript can be placed only in <head>…</head> tags of HTML file Or in <body>…</body> It works automatically when you write your

JavaScript in <body>…</body> JavaScript statements which are written in

<head>…</head> start working when you start calling it by event handler.

Try out! How? In your js-file, write the script below

using Notepad and save your file as abc1.js:

In your HTML file, write:

This is equivalent to:

Previous slide result in what’s shown next slide:

When you click OK you see:

You can place JavaScript right into event handlers.

Event handlers are HTML tag attributes that refer to a specific action which takes place in reference to that form element.

Those include:onClick, onDblClick, onMouseDown, onMouseUp, onMouseOver, onMouseMove, onMouseOut, onKeyPress, onKeyDown, and onKeyUp

Type the followings, then save it as test.html.

NetScape Navigator displays what’s in previous slide as:

JavaScript is a language JavaScript is not Java You use it to write a Web page. You can put it in:

<head>…</head> or <body>…</body> of an HTML file.

short statements resembling URLs You can use a separate js-file and

include it in your HTML file.