JavaScript

General Introduction

JavaScript is a programming language commonly used in web development. It was originally developed by Netscape as a means to add dynamic and interactive elements to websites.

JavaScript is a client-side scripting language, which means the source code is processed by the client's web browser rather than on the web server. This means JavaScript functions can run after a webpage has loaded without communicating with the server. For example, a JavaScript function may check a web form before it is submitted to make sure all the required fields have been filled out. The JavaScript code can produce an error message before any information is actually transmitted to the server.

JavaScript Versions

There have been several formal versions of JavaScript.

• 1.0 Netscape 2

• 1.1 Netscape 3 and Explorer 3

• 1.2 Early Version 4 browsers

• 1.3 Early Version 4 browsers and Version 5 browsers

• 1.4 Netscape Servers

• 1.5 Current version

 Security

• JavaScript cannot read files from or write them to the file system on the computer.

• JavaScript cannot execute any other programs

• JavaScript cannot establish any connection to whatever computer, except to download a new HTML page or to send mail. This, too, would create unacceptable hazards

 Sample Code

Basic JavaScript function that adds two numbers

<script>

function addNumbers(x,y)

{

  return x+y; 

}

var ans = addNumbers(5,6);

console.log(ans);

</script>