Java Script1

JAVA SCRIPT INTRODUCTION Java script is a scripting language developed jointly by SUN and NETSCAPE and meant for the WWW. A scripting language is a simple scripr based programming language designed to enable programmers to write useful programs quickly. A script is similar to a macro which tells a program how to perform a specific procedure. JAVA SCRIPT FACTS •

Java Script is Embedded into HTML

JavaScript code is usually embedded in to a HTML document and is executed within them. By itself Java Script has no user interface. It relies on HTML to provide the means of interaction with the user. Most of Java Script extends the capabilities of HTML by providing events driven code to execute it. • JavaScript Is Browser Dependent Java Script depends on the web browser to support it. If the browser doesn’t support it. Java Script code will be ignored. Internet Explorer 3.0 and Netscape Navigater 2.0 Onwords support Java Script.

•

Java Script is an Interpreated Language

Java Script is interpreated at runtime by the browser before it is executed. It is not compiled into a separate program like a .exe but remains part of the HTML file. •

Java Script is a Loosely Typed Language

Java Script is very flexible compared to java. You need not specify the data type of a variable while declaring it. Also, you need not declare varisble explicitly. It is perfectly legal to declare variable as and when you require them. You can also change the variable data type runtime. •

Java Script Is an Object-Baced Language

Java Script is as object baced language. You can work with objects that encapsulate data and behavior. However JavaScript object model is instance-baced and there is no inheritance. This is the basic difference between an object oriented and an object baced language. •

JavaScript Is Event-Driven

HTML object such as buttons are enhanced to support event handler. You can specify the functionality of a button. •

JavaScript is not Java

Java applet is stored in a separate file and connected to a HTML file through the tag, and it is a strongly typed , objected oriented language. JavaScript is loosely typed object baced, interpreted language meant to create scripts.

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JavaScript Is Multifunctional JavaScript can be used to

1.

Enhance HTML pages.

2.

Develop client side applications.

3. Build to a certain extent client/server Web applications. 4.

Create extensions to a Web server.

5.

Provide databace connectivity without using CGI.

•

JavaScript is Evovling

JavaScript evolved in December 1995. As the times goes by JavaScript will be enhanced and new feaatures added to it. •

JavaScript Language Spans Contexts

JavaScript can be used in server side Netscape Live Wire Pro environment and Microsoft’s Active X server frame work. It is not just a client side scripting tool. WEB APPLICATIONS FRAME WORK •

Client Side frme Work The client side frame work includes the following

 WebBrowser.  HTML 

Client side extensions(Java Applets, Active X Controls and Netscape Plug-Ins)



Scripting Languages(JavaScript & VB Script).



JavaScript role in Web applications development.

•

Client Side Applications

JavaScript has good capabilities when working with HTML tags & associated objects compared to Java. For certain cases JavaScript provides a programming backone with to develop applications. •

Smart Pro Support

Multi frame windows are powerful means of presentation for the Web JavaScript provides means to contain them.

•

Data Validation

JavaScript provides the means for basic data validation before it is sent to the server. Whenever the values entered are correct or whether all fields in a form are filled out or not can be checked before sending data to Web Server. If JavaScript is not used then the data is sent to a Web Server and the Web Server would respond with a message that the data sent to it is incorrect or incomplete. Thus JavaScript ensures data validation and thereby also reduces network traffic. •

Creating Interactive Forms

You can enliven HTML tables can be used to minimize the need to access the server. They are generated and maintained by JavaScript. •

State Maintenance

Since Web is stateless, JavaScript can be used to help maintain state exchanges between the client and Web Server. This is done through cookies. JavaScript provides means to store and retrive cookies.

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