javascript

Javascript is a lightweight, dynamic scripting language, most commonly used as a part of web pages, whose implementations allow client-side script to interact with the user and make dynamic pages. It is an interpreted programming language with object-oriented capabilities.JavaScript is a lightweight, interpreted programming language.

• Designed for creating network-centric applications.
• Complementary to and integrated with Java.
• Complementary to and integrated with HTML.
• Open and cross-platform

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 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

• 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-and-drop components and sliders to give a Rich Interface to your site visitors.

Limitations 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 for security reasons.
• JavaScript cannot be used for networking applications because there is no such support available.
• JavaScript doesn't have any multithreading or multiprocessor capabilities.

SYNTAX

JavaScript can be implemented using JavaScript statements that are placed within the <script>... </script> HTML tags in a web page. You can place the <script> tags, containing your JavaScript, anywhere within your web page, but it is normally recommended that you should keep it within the <head> tags.

The <script> tag alerts the browser program to start interpreting all the text between these tags as a script. A simple syntax of your JavaScript will appear as follows.

<script ...>

           JavaScript code

</script>

The script tag takes two important attributes −

• Language − This attribute specifies what scripting language you are using. Typically, its value will be javascript. Although recent versions of HTML (and XHTML, its successor) have phased out the use of this attribute.
• Type − This attribute is what is now recommended to indicate the scripting language in use and its value should be set to "text/javascript".

So your JavaScript segment will look like −

<script language="javascript" type="text/javascript">

   JavaScript code

</script>

First JavaScript Script

This function can be used to write text, HTML, or both. Take a look at the following code.

<html>

   <body>

      <script language="javascript" type="text/javascript">

            document.write("Hello javascript!")

       </script>

   </body>

</html>

This code will produce the following result − Hello javascript!