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Chapter 1- Overview of JavaScript - Technology369kk

 Overview of JavaScript

JavaScript: 

Ans: JavaScript is a dynamic dynamic programming language, It is lightweight and most commonly used as a part of web pages, whose implementations allow client side script to intract with the user and make dynamic pages. It is an interpreted programming language with object oriented capabilities, this is common features of javascript. 

So in this chapter we are dicuss about details in Javascript, What, Why, How to use and features with advantage and disadvantage and accourding technology369kk, let's begin start now.



Introduction of JavaScript: 

  • About JavaScript : JavaScript is a dynamic dynamic programming language, It is lightweight and most commonly used as a part of web pages, whose implementations allow client side script to intract with the user and make dynamic pages. It is an interpreted programming language with object oriented capabilities, this is common features of javascript. 
  • History of Java: JavaScript was first known as LiveScript, but NetScape changed its name to Javascript, possibly because of the excitement being generated by Java. JavaScript made its first apperance in Netscape's 2.0 in 1995 with the LiveScript.The general-purpose core of the language has been embedded in Netscape, Intrenet Explorer, and other web browsers.
  • The ECMA-262 specification defined a standard version of the core Javascript language.
    • JavaScript is a lightweight, interpreted programming language. 
    • Desired for creating network centric applications. 
    • Complenmentry to and integrated with Java. 
    • Complementery to and intergrated with HTML. 
    • Open and cross- platform.

Client-Side JavaScript

  • Client side JS is the most common form of the language. The script should be included in or refrenced by an HTML document for the code to be interpreted by the browsers. 
  • It mean that a web page need be a static HTML, but can include programs that intract with the user, control the browser and dynamically create HTML content. 
  • The JS 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. For Example, You might use dynamically create HTML content. 
  • The JavaScript client-side scripts mechnasim provided many advantage over traditional CGI server-side scripts, for example you might JS to check if the user has entered a valid e-mail address in a form filed.
  • 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 the user iniitiates explicity or implicity. 

Advantage of JavaScript

The merits of using JavaScript are: 

  • 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 use JavaScript to iclude such item as drag and drop componies and sliders to give a Rich Interface. 
  • Richer interfaces:  You can use JavaScript to include such items as drag and drop components and sliders to give a Rich Intefaces 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 as does not allow the reading or writing of files. This has been kept for security reason. 
  • JavaScript cannot be used for networking applications becuase there is no such support available. 
  • JavaScript doesn't  have any multithrading or multiprocessor capabilties. 
Once again, JavaScript is a lightweight, interpreted programming language that allows you to build interactivity into otherwise satic HTML pages. 

JavaScript Development Tools:

One of major stength of JS is that it does not require expensive development tools, You can start with a simple text editor such as notepad, Since it is an interpreted langauge inside the context of a web browser, doen't need any compiler. 
To make our life simpler various vendors have come up with very nice JS editing tool. Some of them are listed here. 
  1. Microsoft FrontPage: Microsoft has developed a popular HTML editor called Frontpage. FrontPage also provides web developers with a number of JS toosist in tls to ashe creation of intercative websites. 
  2. Macromedia Dreamwever MX:  Macromedia Dreamweaver MX is a very popular HTML and JS editor in the professional web developement crowd. It provides several features JavaScript componment, intergrates well with databases, and confroms to new standards sich as XHTML and XML. 
  3. MicroMedia HomeSites 5: HomeSite 5 is a well-liked HTML and JS editor from Macrosmedia that can be used to manage personal websites effectively. 

Where is JavaScript Today:

The ECMAScript Edition 5 standard will be the first update to be relased in over four years. JS 2.0 confroms to EDition 5 of the ECMAScript standard, and the diffrence between the two is extermenly minor. 
The specification for JavaScript 2.0 can be found on the following site: http: excmascript.org// 

Today, Netscape's JS and Microsoft JScript conform to the ECMAScript standard, althogh both the language still support support the features that are not a part of the standard. 




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