Definition of JavaScript
• JavaScript is an easy-to-use programming language like other programming language
• It is an interpreted language like other programming language.
• It is object-oriented programming.
• It is widely used and supported in various browser
• It is accessible and understandable to the beginner
JavaScript Allows
• Improve appearance in client site
• Especially graphics maintains
• Visual feedback of client site
• Easily Site-to-site navigation
• Perform calculations
• Validation of input and other controls
• Other technologies
Learning JavaScript
• Special syntax to learn but similar to other programming language
• Learn the basics and then use other peoples ideas interact ot your ideas(lots of free sites)
• Write it in a text editor with HTML file , view results in any browser sopurted by the javascript version
• You need to revise your HTML to ensure that no error is occurred
• You need patience and good eyesight as well as thinking.
JavaScript Origins
JavaScript was released by Netscape and Sun Microsystems in 1995.
However, JavaScript is not the same thing as Java
Uses of JavaScript
• Use it to add multimedia elements
• Create pages dynamically and validte various control
• Interact with the user
•JavaScript enhances Web pages with dynamic and interactive features.
•JavaScript runs in client site computer, so less over-headac at server site computer.
•JavaScript 1.3 works with version 4.0 browsers.
Writing JavaScript
JavaScript code is typically embedded in the HTML, to be interpreted and
run by the clients browser. Here are some tips to remember when writing
JavaScript commands.
• JavaScript code is case sensitive
• White space between words and tabs are ignored
• Line breaks are ignored except within a statement
• JavaScript statements end with a semi- colon ;
Javascript supports
JavaScript is supported by Mozilla (from Netscape 2), Explorer (from version 3), Opera (from version 3), Safari, iCab, and Konqueror.
In addition, the following browsers support JavaScript
- Hotjava 3
- WebTV
- OmniWeb
- QNX Voyager
- NetBox
- Amiga-AWeb
- Amiga Voyager
- Sega Dreamcast
- Ant Fresco (Risc)
- as well as several mobile phone browser
Security
Client–side JavaScript has expressly been developed for use in a web browser in conjunction with HTML pages. This has certain consequences for security.
First of all, please note carefully what happens when a user visits a JavaScript–enhanced web site:
The user asks for a certain HTML page without knowing whether it contains JavaScript. The HTML page is delivered to the browser, including the scripts. The scripts usually run automatically when the page loads or when the user takes a certain action. In general the user can’t do anything to stop the scripts (well, he could turn off JavaScript, but few end users know how to do this, or that it can be done, or that JavaScript exists).
So basically an innocent end user downloads a random program and allows it to be executed on his machine. Therefore there should be strict rules as to what this program can and cannot do.
Javascript is a programming language as like others that is used to make web pages interactive. It runs on your client computer and so does not require constant downloads from your web site. It save time of reloading from server.
Javascript cannot do
- JavaScript cannot read or write files from/to other computer.. This would be a clear security hazard
- JavaScript cannot execute any other programs. This would also be unacceptable
- JavaScript cannot establish any connection to any computer or database. It can only download a new HTML or to send mail. This, too, would create unacceptable hazards:
FAQ
Are Javascript and Java the same?:
No, only their names are similar.
What do I need to run Javascript?:
If client computer suport javascript, then no need to run javascript externally.
Why Use JavaScript?
JavaScript enhances Web pages with dynamic and interactive features.
JavaScript runs in client software so no overheadac to server.
JavaScript 1.3 works with version 4.0 browsers.
Do I need to learn Javascript to be able to use it?:
No, You need not. If you want to write javascript code to your page then you will need as a programmer.
What do I need to write Javascript?:
You can write javascript code by any plain text editor such as notepad. But you have to save the codes as .js extension.
Can I use HTML instead of Javascript?:
No. HTML and Javascript are two completely different things. HTML is a markup language. You can only create static web page by HTML. Javascript is a programming language designed for performing dynamic tasks. By using javascript performance of web site increase dynamically.
Can I use PHP or some other server side language instead of Javascript?:
It depands on your tasks.
Perhaps, it depends on where the code needs to run. If it can run before the page loads you can use a server side language. If it has to run after the page has loaded then you must use Javascript as this is the only scripting language supported by all web browsers that support client side scripting.
Does the Javascript go in the same file as the HTML?:
It can but your scripts will be more easily reused on multiple pages of your site if you place them in separate files (using a .js extension helps identify them as Javascript). You then just link the Javascript to your HTML by inserting a <script> tag. The same Javascript can then be added to several pages just by adding the appropriate tag into each of the pages to set up the link.
