Tài liệu Wrox.Professional.JavaScript.For.Web.Developers.2nd.Edition.Jan.2009.eBook-ELOHiM doc

for Web Developers, 2nd Edition Enhance Your Knowledge Advance Your Career Professional JavaScript for Web Developers, 2nd Edition 978-0-470-22780-0This updated bestseller offers an in-

for Web Developers, 2nd Edition

Enhance Your Knowledge Advance Your Career

Professional JavaScript for Web Developers, 2nd Edition

978-0-470-22780-0This updated bestseller offers an in-depth look at the JavaScript language, and covers such topics as debugging tools in Microsoft Visual Studio, FireBug, and Drosera; client-side data storage with cookies, the DOM, and Flash; client-side graphics with JavaScript including SVG, VML, and Canvas; and design patterns including creational, structural, and behavorial patterns

Professional Ajax, 2nd Edition

978-0-470-10949-6

Professional Ajax, 2nd Edition is written for Web application developers

looking to enhance the usability of their web sites and Web applications and intermediate JavaScript developers looking to further understand the language This second edition is updated to cover Prototype, jQuery, FireBug, Microsoft Fiddler, ASP.NET AJAX Extensions, and much more

Concise Guide to Dojo

978-0-470-45202-8Dojo has rapidly become one of the hottest JavaScript based Web development frameworks It provides you with the power and flexibility to create attractive and useful dynamic Web applications quickly and easily

In this fast-paced, code-intensive guide, you’ll discover how to quickly start taking advantage of Dojo The pages are packed with useful information and insightful examples that will help you

Beginning JavaScript and CSS Development with jQuery

978-0-470-22779-4

Beginning JavaScript and CSS Development with jQuery presents the

world of dynamic Web applications to Web developers from the standpoint

of modern standards The author shows new JavaScript developers how working with the standard jQuery library will help them to do more with less code and fewer errors

Beginning JavaScript, 3rd Edition

978-0-470-05151-1This book aims to teach you all you need to know to start experimenting with JavaScript: what it is, how it works, and what you can do with it Starting from the basic syntax, you'll move on to learn how to create powerful Web applications

Beginning CSS, 2nd Edition

978-0-470-17708-2Updated and revised, this book offers a hands-on look at designing standards-based, large-scale, professional-level CSS Web sites Understand designers’ processes from start to finish and gain insight into how designers overcome a site’s unique set of challenges and obstacles Become comfortable with solving common problems, learn the best practices for using XHMTL with CSS, orchestrate a new look for a blog, tackle browser-compatibility issues, and develop functional navigational structures

Introduction xxix

Chapter 1: What Is JavaScript? 1

Chapter 2: JavaScript in HTML 13

Chapter 3: Language Basics 23

Chapter 4: Variables, Scope, and Memory 79

Chapter 5: Reference Types 97

Chapter 6: Object-Oriented Programming 151

Chapter 7: Anonymous Functions 183

Chapter 8: The Browser Object Model 201

Chapter 9: Client Detection 229

Chapter 10: The Document Object Model 261

Chapter 11: DOM Levels 2 and 3 317

Chapter 12: Events 365

Chapter 13: Scripting Forms 433

Chapter 14: Error Handling and Debugging 465

Chapter 15: XML in JavaScript 515

Chapter 16: ECMAScript for XML 547

Chapter 17: Ajax and JSON 567

Chapter 18: Advanced Techniques 589

Chapter 19: Client-Side Storage 617

Chapter 20: Best Practices 635

Chapter 21: Upcoming APIs 669

Chapter 22: The Evolution of JavaScript 703

Appendix A: JavaScript Libraries 759

Appendix B: JavaScript Tools 765

Index 773

JavaScript ® for Web Developers

2nd Edition

JavaScript ® for Web Developers

2nd Edition

Nicholas C Zakas

Wiley Publishing, Inc.

Copyright © 2009 by Wiley Publishing, Inc., Indianapolis, Indiana

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mom, dad, Greg, Yiayia, and Papou

We may be few in numbers, but we are mighty!

Your constant love and support have made the past couple of years possible.

Nicholas C Zakas has a B.S in Computer Science from Merrimack College and an M.B.A from Endicott

College He is the coauthor of Professional Ajax, Second Edition (Wiley, 2007) as well as dozens of online

articles Nicholas works for Yahoo! as a principal front-end engineer on Yahoo!’s front page and a

contributor to the Yahoo! User Interface (YUI) Library He has worked in web development for more than eight years, during which time he has helped develop web solutions in use at some of the largest

companies in the world

Nicholas can be reached through his web site www.nczonline.net

Vice President and Executive Group PublisherRichard Swadley

Vice President and Executive PublisherJoseph B Wikert

Project Coordinator, CoverLynsey Stanford

ProofreaderKathryn Duggan

IndexerJack Lewis

It takes many people to create a single book, and I’d like to thank some people here for their

contributions to this work

First and foremost, thanks to everyone at Wiley for their support: Jim Minatel for once again putting his faith in me; Kevin Kent for dealing with the hectic outline rearrangements I tend to make throughout writing; and Alexei Gorkov, the best technical editor in the world, who makes sure that everything I say

is 100-percent accurate

A big thanks to everyone who provided feedback on draft chapters: David Serduke, Julian Turner, Pete Frueh, Chris Klaiber, Stoyan Stefanov, Ross Harmes, and David Golightly Your early feedback was really helpful in making this book what it is today

Last, thanks to Eric Miraglia for his contribution of a foreword Eric is the reason I ended up at Yahoo!, and it has been a pleasure to work with him for the past two years

Foreword xxvii Introduction xxix

Chapter 1: What Is JavaScript? 1

JavaScript Implementations 3

The Boolean Type 30

Chapter 4: Variables, Scope, and Memory 79

Primitive and Reference Values 79

Execution Context and Scope 84

Primitive Wrapper Types 130

Summary 149

Chapter 6: Object-Oriented Programming 151

Mimicking Block Scope 191

Summary 199

Chapter 8: The Browser Object Model 201

The location Object 216

Summary 258

Chapter 10: The Document Object Model 261

Event Handlers or Listeners 368

Mutation Events 402

Memory and Performance 422

Scripting Select Boxes 450

Summary 464

Chapter 14: Error Handling and Debugging 465

Browser Error Reporting 465

Common Internet Explorer Errors 492

XML DOM Support in Browsers 515

XPath Support in Browsers 530

Chapter 18: Advanced Techniques 589

Performance 647

Appendix A: JavaScript Libraries 759

Appendix B: JavaScript Tools 765

Index 773

JavaScript, for much of its existence, has been the subject of fear, invective, disdain, and

misunderstanding In its early years, many “serious programmers” thought that JavaScript wasn’t

serious enough

By contrast, many liberal arts majors drafted into web-developer service during the dotcom boom

thought JavaScript was mysterious and arcane Many who had both the tenacity and the patience to fully grok JavaScript as a language were nevertheless frustrated by its inconsistent implementation across competing browsers All of these factors helped lead to a proliferation of awkward and poorly conceived scripts And, through the extraordinary openness of front-end code on the Web, a lot of bad habits were copied from one site and pasted into the source of another Thus JavaScript’s bad reputation as a

language, which was generally ill-deserved, became intertwined with a deservedly bad reputation

surrounding its implementations

Around 2001 (with the release of Internet Explorer 6), improved browser implementations and

improving practice in web development began to converge The XMLHttpRequest object at the heart of Ajax was slowly being discovered, and a new paradigm of desktop-style user interaction was emerging within the browser The DOM APIs that allowed JavaScript to manipulate the structure and content of web documents had solidified CSS, for all the contortions, omissions, and the willful insanity of its

implementations by browser vendors, had progressed far enough that beauty and responsiveness could

be combined with the Web’s new interactive power As a result, JavaScript became the subject of a new set of emotions: surprise, delight, and awe If you think back to the first time you used Google Maps in

2004, you may recall the feeling

Google Maps was among an emerging class of applications that took browser-based programming as seriously as back-end programming and made us think differently about the application canvas provided

by the web browser (Oddpost, which provided Outlook-style email functionality in a webmail client as early as 2003, was another notable pioneer.) The proliferation of these applications and the increasing market penetration of browsers that supported them led to a genuine renaissance in web application

engineering “Web 2.0” was born, and Ajax became the “it” technology The Web was suddenly interesting all over again JavaScript, as the only programming language of the Web, became more interesting, too

Interesting, but hard to do well JavaScript and its companion APIs in the Document Object Model (DOM) and Browser Object Model (BOM) were inconsistently implemented, making cross-browser

implementations vastly more difficult than they needed to be The profession of front-end engineering was still young University curricula had not (and still have not) stepped in to meet the training challenge

JavaScript, arguably the most important programming language in the world by the end of 2004, was not

a first-class subject in the academic sense of the word A new day was dawning on the Web, and there was a serious question as to whether there would be enough knowledgeable, well-informed engineers to meet the new challenges

Many technical writers stepped in to fill the gap with books on JavaScript There were dozens of these over the years, but by and large they were a disappointing lot Some of them promoted techniques that

were relevant only in retrograde browsers; some promoted techniques that were easy to cut and paste

but hard to extend and maintain Puzzlingly, many books on JavaScript seemed to be written by people

who didn’t really like JavaScript, who didn’t think you should like it, and who weren’t optimistic about

your ability to understand it fully

One of the genuinely good books in the world of front-end engineering arrived when Nicholas C Zakas

published the first edition of Professional JavaScript for Web Developers in 2005 At the time, my colleagues

and I were working at Yahoo! to create the Yahoo! User Interface Library (YUI) as a foundation for

front-end engineering here and to evangelize best practices in our nascent discipline Every Friday, we’d

gather in a classroom to talk about the front-end engineering and to teach classes on JavaScript, CSS, and

the creation of web applications in the browser We carefully reviewed the offerings at the time for books

that would help new engineers learn how to build robust, standards-based, easy-to-maintain web

applications using advanced JavaScript and DOM scripting As soon as it was published, Zakas’s book

became our textbook for JavaScript

We’ve been using it ever since We thought so highly of the book that we talked Zakas into coming to

Yahoo! to help shape the front-end engineering community here

What Zakas accomplished with Professional JavaScript for Web Developers is singular: He treated JavaScript

as a subject that is both serious and accessible If you are a programmer, you will learn where JavaScript

fits into the broader spectrum of languages and paradigms with which you’re familiar You’ll learn how

its system of inheritance and its intrinsic dynamism are, yes, unconventional but also liberating and

powerful You’ll learn to appreciate JavaScript as a language from a fellow programmer who respects it

and understands it

If you’re one of those liberal arts majors who was drawn into this profession in the boom years and never

left, and if you want to fill in the gaps of your understanding of JavaScript, you’ll find Zakas to be the

mentor you’ve always wanted — the one who will help you make the transition from “making things

work” to “making things that work well.” He’ll leave you with a serious understanding of a serious subject

Best of all, you’ll find that he doesn’t pander to preconceived notions about how deeply you should

understand the language He takes it seriously, and in a patient, accessible way he helps you to do the same

This second edition of Professional JavaScript for Web Developers — expanded, updated, improved — drops

some subjects that are less relevant to the profession today and upgrades the rest with what we’ve

learned between 2005 and 2008 These years have been important ones, and Zakas is on the front line of

the process of learning He’s spent those years architecting the current generation of the Web’s most

popular personal portal (My Yahoo!) and the next version of the web’s most visited site (Yahoo!’s front

page) Insights forged in these complex, ultra-high-volume applications inform every page of this new

volume, all passed through Zakas’s unique filter as a teacher/author

As a result, his solutions go beyond being book-smart and include the kind of practical wisdom you can

only get by living and breathing code on a daily basis

And that’s seriously good news for the rest of us Professional JavaScript for Web Developers is now even

better, even more relevant, and even more important to have on your shelf

Eric Miraglia, Ph.D

Sr Engineering Manager, Yahoo! User Interface Library (YUI)Sunnyvale, California

Introduction

Some claim that JavaScript is now the most popular programming language in the world, running any number of complex web applications that the world relies on to do business, make purchases, manage processes, and more

JavaScript is very loosely based on Java, an object - oriented programming language popularized for use on the Web by way of embedded applets Although JavaScript has a similar syntax and programming methodology,

it is not a “ light ” version of Java Instead, JavaScript is its own dynamic language, finding its home in web browsers around the world and enabling enhanced user interaction on web sites and web applications alike

In this book, JavaScript is covered from its very beginning in the earliest Netscape browsers to the

present - day incarnations flush with support for the DOM and Ajax You learn how to extend the

language to suit specific needs and how to create seamless client - server communication without

intermediaries such as Java or hidden frames In short, you learn how to apply JavaScript solutions to business problems faced by web developers everywhere

What Does This Book Cover?

Professional JavaScript for Web Developers , 2nd Edition, provides a developer - level introduction along with

the more advanced and useful features of JavaScript

Starting at the beginning, the book explores how JavaScript originated and evolved into what it is today

A detailed discussion of the components that make up a JavaScript implementation follows, with specific focus on standards such as ECMAScript and the Document Object Model (DOM) The differences in JavaScript implementations used in different popular web browsers are also discussed

Building on that base, the book moves on to cover basic concepts of JavaScript, including its version of object - oriented programming, inheritance, and its use in various markup languages such as HTML An

in - depth examination of events and event handling is followed by an exploration of browser-detection techniques and a guide to using regular expressions in JavaScript The book then takes all this

knowledge and applies it to creating dynamic user interfaces

The last part of the book is focused on advanced topics, including performance and memory

optimization, best practices, and a look at where JavaScript is going in the future

Who Is This Book For?

This book is aimed at the following three groups of readers:

Experienced developers familiar with object - oriented programming who are looking to learn JavaScript as it relates to traditional object-oriented (OO) languages such as Java and C++

Web application developers attempting to enhance the usability of their web sites and web applications

❑

❑

In addition, familiarity with the following related technologies is a strong indicator that this book is for

This book is not aimed at beginners who lack a basic computer-science background or those looking to

add some simple user interactions to web sites These readers should instead refer to Wrox ’ s Beginning

JavaScript, 3rd Edition (Wiley, 2007)

What You Need to Use This Book

To run the samples in the book, you need the following:

Windows 2000, Windows Server 2003, Windows XP, Vista, or Mac OS X

Internet Explorer 6 or higher, Firefox 2 or higher, Opera 9 or higher, Chrome 0.2 or higher, or

Safari 2 or higher

The complete source code for the samples is available for download at www.wrox.com/

How This Book Is Str uctured

This book comprises the following chapters:

Chapter 1, What Is JavaScript? — Explains the origins of JavaScript: where it came from, how it

evolved, and what it is today Concepts introduced include the relationship between JavaScript and

ECMAScript, the Document Object Model (DOM), and the Browser Object Model (BOM) A discussion

of the relevant standards from the European Computer Manufacturer ’ s Association (ECMA) and the

World Wide Web Consortium (W3C) is also included

Chapter 2, JavaScript in HTML — Examines how JavaScript is used in conjunction with HTML to

create dynamic web pages This chapter introduces the various ways of embedding JavaScript into a

page, including a discussion surrounding the JavaScript content - type and its relationship to the

< script > element

Chapter 3, Language Basics — Introduces basic language concepts, including syntax and flow control

statements This chapter explains the syntactic similarities of JavaScript and other C - based languages

and points out the differences Type coercion is introduced as it relates to built - in operators

Chapter 4, Variables, Scope, and Memory — Explores how variables are handled in JavaScript given

their loosely typed nature A discussion about the differences between primitive and reference values

is included, as is information about execution context as it relates to variables Also, a discussion about garbage collection in JavaScript explains how memory is reclaimed when variables go out of scope

Chapter 5, Reference Types — Covers all of the details regarding JavaScript ’ s built - in reference types,

such as Object and Array Each reference type described in ECMA - 262 is discussed both in theory and how it relates to browser implementations

Chapter 6, Object - Oriented Programming — Explains how to use object - oriented (OO) programming

in JavaScript Since JavaScript has no concept of classes, several popular techniques are explored for object creation and inheritance Also covered in this chapter is the concept of function prototypes and how that relates to an overall OO approach

Chapter 7, Anonymous Functions — Explores one of the most powerful aspects of JavaScript:

anonymous functions Topics include closures, how the this object works, the module pattern, and creating private object members

Chapter 8, The Browser Object Model — Introduces the Browser Object Model (BOM), which is

responsible for objects allowing interaction with the browser itself Each of the BOM objects is covered, including window , document , location , navigator , and screen

Chapter 9, Client Detection — Explains various approaches to detecting the client machine and its

capabilities Different techniques include capability detection and user - agent string detection This chapter discusses the pros and cons as well as the situational appropriateness of each approach

Chapter 10, The Document Object Model — Introduces the Document Object Model (DOM) objects

available in JavaScript as defined in DOM Level 1 A brief introduction to XML and its relationship to the DOM gives way to an in - depth exploration of the entire DOM and how it allows developers to manipulate a page

Chapter 11, DOM Levels 2 and 3 — Builds on the previous chapter, explaining how DOM Levels 2

and 3 augmented the DOM with additional properties, methods, and objects Compatibility issues between Internet Explorer and other browsers are discussed

Chapter 12, Events — Explains the nature of events in JavaScript, where they originated, legacy

support, and how the DOM redefined how events should work A variety of devices are covered,

including the Wii and iPhone

Chapter 13, Scripting Forms — Looks at using JavaScript to enhance form interactions and work

around browser limitations The discussions in this chapter focus on individual form elements such as text boxes and select boxes and on data validation and manipulation

Chapter 14, Error Handling and Debugging — Discusses how browsers handle errors in JavaScript

code and presents several ways to handle errors Debugging tools and techniques are also discussed for each browser, including recommendations for simplifying the debugging process

Chapter 15, XML in JavaScript — Presents the features of JavaScript used to read and manipulate

eXtensible Markup Language (XML) data This chapter explains the differences in support and objects in various web browsers, and offers suggestions for easier cross - browser coding This chapter also covers

Chapter 16, ECMAScript for XML — Discusses the ECMAScript for XML (E4X) extension to

JavaScript, which is designed to simplify working with XML This chapter explains the advantages of

E4X over using the DOM for XML manipulation

Chapter 17, Ajax and JSON — Looks at common Ajax techniques, including the use of the

XMLHttpRequest object and Internet Explorer ’ s XDomainRequest object for cross - domain Ajax This

chapter explains the differences in browser implementations and support as well as recommendations

for usage

Chapter 18, Advanced Techniques — Dives into some of the more complex JavaScript patterns,

including function currying, partial function application, and dynamic functions This chapter also

covers creating a custom event framework to enable simple event support for custom objects

Chapter 19, Client - Side Storage — Discusses the various techniques for storing data on the client

machine This chapter begins with a discussion of the most commonly supported feature, cookies, and

then discusses newer functionality such as DOM storage

Chapter 20, Best Practices — Explores approaches to working with JavaScript in an enterprise

environment Techniques for better maintainability are discussed, including coding techniques,

formatting, and general programming practices Execution performance is discussed and several

techniques for speed optimization are introduced Last, deployment issues are discussed, including

how to create a build process

Chapter 21, Upcoming APIs — Introduces APIs being created to augment JavaScript in the browser

Even though these APIs aren ’ t yet complete or fully implemented, they are on the horizon and

browsers have already begun partially implementing their features This chapter includes discussions

on the Selectors API and HTML 5

Chapter 22, The Evolution of JavaScript — Looks into the future of JavaScript to see where the

language is headed ECMAScript 3.1, ECMAScript 4, and ECMAScript Harmony are discussed

Conventions

To help you get the most from the text and keep track of what ’ s happening, a number of conventions are

used throughout this book

Boxes like this one hold important, not - to - be forgotten information that is directly

relevant to the surrounding text

Notes, tips, hints, tricks, and asides to the current discussion are offset and placed in italics like this

As for styles in the text:

N ew terms and important words are italicized when they’re introduced

K eyboard combinations are shown like this: Ctrl+A

F ile names, URLs, and code within the text look like this: persistence.properties

❑

❑

❑

C ode is presented in two different ways:

Monofont type with no highlighting is used for most code examples

Gray highlighting is used to emphasize code that’s particularly important in the present context

Source Code

As you work through the examples in this book, you may choose either to type in all the code manually

or to use the source code files that accompany the book All of the source code used in this book is

available for download at www.wrox.com Once at the site, simply locate the book ’ s title (either by using the Search box or by using one of the title lists) and click the Download Code link on the book ’ s detail page to obtain all the source code for the book

Because many books have similar titles, you may find it easiest to search by ISBN This book ’ s ISBN is

978 - 0 - 470 - 22780 - 0

After you download the code, just decompress it with your favorite compression tool Alternately, you can go to the main Wrox code download page at www.wrox.com/dynamic/books/download.aspx to see the code available for this book and all other Wrox books

Errata

We make every effort to ensure that there are no errors in the text or in the code However, no one is perfect, and mistakes do occur If you find an error in one of our books, such as a spelling mistake or faulty piece of code, we would be very grateful for your feedback By sending in errata, you may save another reader hours of frustration and help us provide even higher - quality information

To find the errata page for this book, go to www.wrox.com and locate the title using the Search box or one

of the title lists Then, on the book details page, click the Book Errata link On this page you can view all errata that has been submitted for this book and posted by Wrox editors A complete book list, including links to each book ’ s errata, is also available at www.wrox.com/misc - pages/booklist.shtml

If you don ’ t spot “ your ” error on the Book Errata page, go to www.wrox.com/contact/techsupport

.shtml and complete the form there to send us the error you have found We ’ ll check the information and, if appropriate, post a message to the book ’ s errata page and fix the problem in subsequent editions of the book

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For author and peer discussion, join the P2P forums at p2p.wrox.com The forums are a web - based

system for you to post messages relating to Wrox books and related technologies, as well as to interact with other readers and technology users The forums offer a subscription feature to e - mail you topics of interest of your choosing when new posts are made to the forums Wrox authors, editors, other industry experts, and your fellow readers are present on these forums

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At http://p2p.wrox.com , you will find a number of different forums that will help you not only as you

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JavaScript ® for Web Developers

2nd Edition

What Is JavaScript?

When JavaScript first appeared in 1995, its main purpose was to handle some of the input

validation that had previously been left to server - side languages such as Perl Prior to that time, a

round - trip to the server was needed to determine if a required field had been left blank or an

entered value was invalid Netscape Navigator sought to change that with the introduction of

JavaScript The capability to handle some basic validation on the client was an exciting new feature

at a time when use of telephone modems was widespread The associated slow speeds turned

every trip to the server into an exercise in patience

Since that time, JavaScript has grown into an important feature of every major web browser on the

market No longer bound to simple data validation, JavaScript now interacts with nearly all

aspects of the browser window and its contents JavaScript is recognized as a full programming

language, capable of complex calculations and interactions, including closures, anonymous

(lambda) functions, and even metaprogramming JavaScript has become such an important part of

the Web that even alternative browsers, including those on mobile phones and those designed for

users with disabilities, support it Even Microsoft, with its own client - side scripting language

called VBScript, ended up including its own JavaScript implementation in Internet Explorer from

its earliest version

The rise of JavaScript from a simple input validator to a powerful programming language could

not have been predicted JavaScript is at once a very simple and very complicated language that

takes minutes to learn but years to master To begin down the path to using JavaScript ’ s full

potential, it is important to understand its nature, history, and limitations

A Shor t Histor y

Around 1992, a company called Nombas (later bought by Openwave) began developing an

embedded scripting language called C - minus - minus (Cmm for short) The idea behind Cmm was

simple: a scripting language powerful enough to replace macros, but still similar enough to C (and

C++) that developers could learn it quickly This scripting language was packaged in a shareware

product called CEnvi, which first exposed the power of such languages to developers Nombas

eventually changed the name Cmm to ScriptEase ScriptEase became the driving force behind Nombas

products When the popularity of Netscape Navigator started peaking, Nombas developed a version of

CEnvi that could be embedded into web pages These early experiments were called Espresso Pages , and

they represented the first client - side scripting language used on the World Wide Web Little did Nombas

know that its ideas would become an important foundation for the Internet

As the Web gained popularity, a gradual demand for client - side scripting languages developed At

the time, most Internet users were connecting over a 28.8 kbps modem even though web pages were

growing in size and complexity Adding to users ’ pain was the large number of round - trips to the server

required for simple form validation Imagine filling out a form, clicking the Submit button, waiting

30 seconds for processing, and then being met with a message indicating that you forgot to complete a

required field Netscape, at that time on the cutting edge of technological innovation, began seriously

considering the development of a client - side scripting language to handle simple processing

Brendan Eich, who worked for Netscape at the time, began developing a scripting language called

LiveScript for the release of Netscape Navigator 2 in 1995, with the intention of using it both in the

browser and on the server (where it was to be called LiveWire) Netscape entered into a development

alliance with Sun Microsystems to complete the implementation of LiveScript in time for release Just

before Netscape Navigator 2 was officially released, Netscape changed LiveScript ’ s name to JavaScript to

capitalize on the buzz that Java was receiving from the press

Because JavaScript 1.0 was such a hit, Netscape released version 1.1 in Netscape Navigator 3 The

popularity of the fledgling Web was reaching new heights and Netscape had positioned itself to be

the leading company in the market At this time, Microsoft decided to put more resources into a

competing browser named Internet Explorer Shortly after Netscape Navigator 3 was released, Microsoft

introduced Internet Explorer 3 with a JavaScript implementation called JScript (so called to avoid any

possible licensing issues with Netscape) This major step for Microsoft into the realm of web browsers in

August 1996 is now a date that lives in infamy for Netscape, but it also represented a major step forward

in the development of JavaScript as a language

Microsoft ’ s implementation of JavaScript meant that there were three different JavaScript versions

floating around: JavaScript in Netscape Navigator, JScript in Internet Explorer, and CEnvi in ScriptEase

Unlike C and many other programming languages, JavaScript had no standards governing its syntax or

features, and the three different versions only highlighted this problem With industry fears mounting, it

was decided that the language must be standardized

In 1997, JavaScript 1.1 was submitted to the European Computer Manufacturers Association

(Ecma) as a proposal Technical Committee #39 (TC39) was assigned to “ standardize the syntax

and semantics of a general purpose, cross - platform, vendor - neutral scripting language ”

( http://www.ecma - international.org/memento/TC39.htm ) Made up of programmers from

Netscape, Sun, Microsoft, Borland, and other companies with interest in the future of scripting, TC39

met for months to hammer out ECMA - 262, a standard defining a new scripting language named

ECMAScript

The following year, the International Organization for Standardization and International Electrotechnical

Commission (ISO/IEC) also adopted ECMAScript as a standard (ISO/IEC - 16262) Since that time,

browsers have tried, with varying degrees of success, to use ECMAScript as a basis for their JavaScript

implementations