Web Mumbai

Introduction
Javascript is an easy-to-use programming language that can be embedded in the header of your web pages. It can enhance the dynamics and interactive features of your page by allowing you to perform calculations, check forms, write interactive games, add special effects, customize graphics selections, create security passwords and more.

• JavaScript was designed to add interactivity to HTML pages
• JavaScript is a scripting language
• A scripting language is a lightweight programming language
• JavaScript is usually embedded directly into HTML pages
• JavaScript is an interpreted language (means that scripts execute without preliminary compilation)
• Everyone can use JavaScript without purchasing a license

JavaScript is a simple programming language that can be written directly into HTML documents to allow for increased interactivity with the user. For example, JavaScript can be used to create online calculators or show the current date and time.

JavaScript is a client side, interpreted, object oriented, high level scripting language, while Java is a client side, compiled, object oriented high level language. Now after that mouthful, here’s what it means.

Client side

Programs are passed to the computer that the browser is on, and that computer runs them. The alternative is server side, where the program is run on the server and only the results are passed to the computer that the browser is on. Examples of this would be PHP, Perl, ASP, JSP etc.

Interpreted

The program is passed as source code with all the programming language visible. It is then converted into machine code as it is being used. Compiled languages are converted into machine code first then passed around, so you never get to see the original programming language. Java is actually dual half compiled, meaning it is half compiled (to ‘byte code’) before it is passed, then executed in a virtual machine which converts it to fully compiled code just before use, in order to execute it on the computer’s processor. Interpreted languages are generally less fussy about syntax and if you have made mistakes in a part they never use, the mistake usually will not cause you any problems.

Scripting

This is a little harder to define. Scripting languages are often used for performing repetitive tasks. Although they may be complete programming languages, they do not usually go into the depths of complex programs, such as thread and memory management. They may use another program to do the work and simply tell it what to do. They often do not create their own user interfaces, and instead will rely on the other programs to create an interface for them. This is quite accurate for JavaScript. We do not have to tell the browser exactly what to put on the screen for every pixel, we just tell it that we want it to change the document, and it does it. The browser will also take care of the memory management and thread management, leaving JavaScript free to get on with the things it wants to do.

High level

Written in words that are as close to english as possible. The contrast would be with assembly code, where each command can be directly translated into machine code.

Object oriented

Probably the most important thing I would like you to take away from this tutorial is the idea that programming in an object oriented language is more than just learning new functions, syntax, etc. OOP is more than learning a new language; it requires a new way of thinking. The idea is to not primarily concentrate on the cornerstones of procedural languages – data structures and algorithms – but instead think in terms of objects.

Tags: JavaScript, javascript tutorial, Object oriented, tutorial