JavaScript Tabriz university 2009. Its September 1995.

JavaScript

Tabriz university2009

Its September

1995

NetscapeVersion 2.0 of

browser is released.

Its first version to come with

the scripting language.

the name of the language was first

Mocha and then, when released,

LiveScript

In December of that year

Netscape made a marketing deal with

Sunand renamed the language to

JavaScript

What is JavaScript?

JavaScript is a client-side scripting language. If the browser supports the

language, JavaScript grants access to the current page and lets the

script determine properties of the client, redirect the user to

another page, access cookies, and do much more.

Microsoft included JavaScript support from Internet Explorer version 3 onward (mid-1996).

For legal reasons the language was called

JScript.

Microsoft started to include additional,

IE-only features to JScript.

In 1997, the standard

ECMAScript (ECMA-262) was published;

JavaScript is therefore the first implementation of that standard.

ECMAScript became an ISO norm in 1998.

ECMA: European Computer Manufacturers Association

Around 1997 or 1998, the browser war between Netscape and Microsoft reached a climax,

with both vendors adding new, incompatible functionality

to version 5 of their browsers.

Netscape scrapped the idea of releasing browser version 5 and decided to start all over with

Netscape 6,

which helped Internet Explorer to

expand its market share to over

90%.

It took the then-founded

Mozilla project several years to come to life again.

The very popular

Firefox browser was based on Mozilla and started to take market

share away from Microsoft.

Other browsers, by the way, support JavaScript as

well. Differences are subtle, but still can be extremely annoying when one is developing a

browser-agnostic web application.

Internet Explorer

Mozilla

• Firefox• Epiphany• Camino• Galeon

Konqueror

Safari

Java Vs JavaScript

Java

• 1991• Sun Microsystems.• Called Oak.

• 1995• Called Java.

Java

A simple, secure, portable, object oriented, robust, multi-threaded, architecture-neutral, interpreted, high performance, distributed and dynamic programming language.

Java Vs JavaScript

• JavaScript was developed by Netscape• Java was developed by Sun

Java Vs JavaScript

• JavaScript–Cannot draw, multi-thread, network or do I/O

• Java–Cannot interact with Browser or control content

JavaScript

• We’ll call collections of JavaScript code

scripts, not programs• JavaScript and Java are only related through

syntax• JavaScript’s support for objects is very

different

Object Orientation and JavaScript

• JavaScript is NOT an object oriented programming language:– Does not support class based inheritance– Cannot support polymorphism

Object Orientation and JavaScript

• JavaScript objects are collections of properties, which are like the members of classes in Java and C++

What is it used for today?

• Handling User Interaction:– Checking for accuracy and appropriateness of

data entry from forms– Doing small calculations/manipulations of forms

input data– Save data as cookie so it is there upon visiting the

page• Reduce web server processing load • Reduce delay when users’ input is wrong

• Generating Dynamic HTML documents• Controlling applets and calling Java from

JavaScript• Accessing JavaScript from Java• Allow further capabilities together with other

technologies:– DHTML ( Dynamic HTML)– AJAX (Asynchronous JavaScript and XML)

Language Basics

JavaScript in HTML

• directly, as in<script type = “text/javaScript">

JavaScript script –</script>

• Or indirectly, as a file specified in the src attribute of <script>, as in

<script type = "text/javaScript"src = "myScript.js">

</script>

Example

<HTML> <BODY> <SCRIPT TYPE=“text/javascript”>  </SCRIPT> </BODY></HTML>

Syntax

• Variables• Functions• Objects• …

• Syntax based on C/C++/Java• Case Sensitive

I need JS code

WRITE

STEAL

References:

• JavaScript™ Phrasebook: Essential Code and Commands– By Christian Wenz– Sams

JavaScript Tabriz university 2009. Its September 1995.

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