Wiley - Professional Ajax (2006).pdf - Ajax - darekisap

Professional Ajax

Nicholas C. Zakas

Jeremy McPeak

Joe Fawcett

Published by Wiley Publishing, Inc.

10475 Crosspoint Boulevard Indianapolis , IN 46256 .

www.wiley.com

Published simultaneously in Canada

ISBN-13: 978-0-471-77778-6

ISBN-10: 0-471-77778-1

0471777781

Manufactured in the United States of America

10 9 8 7 6 5 4 3 2 1

1B/RZ/QR/QW/IN

Library of Congress Cataloging-in-Publication Data

Zakas, Nicholas C.

Professional Ajax / Nicholas C. Zakas, Jeremy McPeak, Joe Fawcett.

p. cm.

Includes index.

ISBN-13: 978-0-471-77778-6 (paper/website)

ISBN-10: 0-471-77778-1 (paper/website)

1. JavaScript (Computer program language) 2. Asynchronous transfer mode. 3. World Wide

Web. I. McPeak, Jeremy, 1979- II. Fawcett, Joe, 1962- III. Title.

QA76.73.J39Z35 2006

005.13'3—dc22

2005034274

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print may not be available in electronic books.

About the Authors

Nicholas C. Zakas has a BS degree in Computer Science from Merrimack College and an MBA

degree from Endicott College. He is the author of Professional JavaScript for Web Developers

as well as several online articles. Nicholas has worked in web development for more than five

years and has helped develop web solutions in use at some of the largest companies in the

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

Jeremy McPeak began tinkering with web development as a hobby in 1998. Currently working

in the IT department of a school district, Jeremy has experience developing web solutions with

JavaScript, PHP, and C#. He has written several online articles covering topics such as XSLT,

WebForms, and C#.

Joe Fawcett started programming in the 1970s and worked briefly in IT after leaving full-time

education. He then pursued a more checkered career before returning to software development

in 1994. In 2003, he was awarded the title Microsoft Most Valuable Professional in XML for

community contributions and technical expertise. Joe currently works in London as a developer

for The Financial Training Company, which provides professional certifications and business

training.

Credits

Senior Acquisitions Editor

Jim Minatel

Development Editor

John Sleeva

Technical Editor

Alexei Gorkov

Production Editor

Kathryn Duggan

Copy Editor

Michael Koch

Editorial Manager

Mary Beth Wakefield

Production Manager

Tim Tate

Vice President and Executive Group Publisher

Richard Swadley

Vice President and Executive Publisher

Joseph B. Wikert

Graphics and Production Specialists

Carrie A. Foster

Lauren Goddard

Joyce Haughey

Jennifer Heleine

Barbara Moore

Melanee Prendergast

Alicia B. South

Quality Control Technician

John Greenough

Proofreading and Indexing

TECHBOOKS Production Services

To my family and Emily, whose love and support have been invaluable over the past couple of

years.

—Nicholas C. Zakas

To my parents, Sheila and William, who instilled in me a love of reading. Thank you!

—Jeremy McPeak

Acknowledgments

It takes many people to create a book such as this, and we'd like to thank some people for their

contributions to this work.

First and foremost, thanks to everyone at Wiley for their support: Jim Minatel for starting the

process, Gabrielle Nabi for helping with the first few chapters, and John Sleeva for finishing

where Gabrielle left off. Also, a big thanks to our technical editor, Alexei Gorkov, for doing a

fantastic job of keeping us honest.

Last, a big thanks to those who provided pre-publication feedback, including Martin Honnen,

Peter Frueh, Mike Shaffer, Brad Neuberg, Steven Peterson, and Eric Miraglia.

Introduction

With recent advances in JavaScript, web developers have been able to create an

unprecedented user experience in web applications. Breaking free of the "click-and-wait"

paradigm that has dominated the web since its inception, developers can now bring features

formerly reserved for desktop applications onto the web using a technique called Ajax.

Ajax is an all-encompassing term surrounding the use of asynchronous HTTP requests initiated

by JavaScript for the purpose of retrieving information from the server without unloading the

page. These requests may be executed in any number of ways and using any number of

different data transmission formats. Combining this remote data retrieval with the interactivity of

the Document Object Model (DOM) has bred a new generation of web applications that seem to

defy all the traditional rules of what can happen on the web. Big companies such as Google,

Yahoo!, and Microsoft have devoted resources specifically towards the goal of creating web

applications that look and behave like desktop applications.

This book covers the various aspects of Ajax, including the different ways you can initiate HTTP

requests to the server and the different formats that can be used to carry data back and forth.

You will learn different Ajax techniques and patterns for executing client-server communication

on your web site and in web applications.

Whom This Book is For

This book is aimed at two groups of readers:

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

applications.

Intermediate JavaScript developers looking to further understand the language.

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

is for you:

XML

XSLT

Web Services

PHP

HTML

CSS

This book is not aimed at beginners without a basic understanding of the aforementioned

technologies. Also, a good understanding of JavaScript is vitally important to understanding this

book. Readers who do not have this knowledge should instead refer to books such as

Beginning JavaScript, Second Edition (Wiley Publishing, ISBN 0-7645-5587-1) and Professional

JavaScript for Web Developers (Wiley Publishing, ISBN 0-7645-7908-8).

What This Book Covers

Professional Ajax provides a developer-level tutorial of Ajax techniques, patterns, and use

cases.

The book begins by exploring the roots of Ajax, covering how the evolution of the Web and new

technologies directly led to the development of Ajax techniques. A detailed discussion of how

frames, JavaScript, cookies, XML, and XMLHttp related to Ajax is included.

After this introduction, the book moves on to cover the implementation of specific Ajax

techniques. Request brokers such as hidden frames, dynamic iframes, and XMLHttp are

compared and contrasted, explaining when one method should be used over another. To make

this discussion clearer, a brief overview of HTTP requests and responses is included.

Once a basic understanding of the various request types is discussed, the book moves on to

provide indepth examples of how and when to use Ajax in a web site or web application.

Different data transmission formats—including plain text, HTML, XML, and JSON—are

discussed for their advantages and disadvantages. Also included is a discussion on web

services and how they may be used to perform Ajax techniques.

The last part of the book walks you through the creation of a full-fledged Ajax web application

called AjaxMail, which incorporates many of the techniques discussed throughout the book, and

introduces you to several Ajax libraries designed to make Ajax communication easier on

developers.

How This Book is Structured

This book begins by providing background about the origins of Ajax before moving into actual

implementation. Next, the various ways to accomplish client-server communication are

discussed, setting the stage for the rest of the book. It is recommended that you read the book

straight through, as each chapter builds on information in the previous chapters.

The chapter-level breakdown is as follows:

Chapter 1 : "What Is Ajax?" This chapter explains the origins of Ajax and the

technologies involved. It describes how Ajax developed as the Web developed and who, if

anyone, can claim ownership of the term and techniques.

Chapter 2 : "Ajax Basics." This chapter introduces the various ways to accomplish

Ajax communication, including the hidden frame technique and XMLHttp. The advantages

and disadvantages of each approach are discussed, as well as guidelines as to when each

should be used.

Chapter 3 : "Ajax Patterns." This chapter focuses on design patterns using Ajax. There

are a variety of ways to incorporate Ajax into web sites and web applications; these have

been organized into a handful of design patterns that describe best practices for Ajax

incorporation.

Chapter 4 : "XML, XPath, and XSLT." This chapter introduces XML, XPath, and XSLT

as complementary technologies to Ajax. The discussion centers on using XML as a data

transmission format and using XPath and XSLT to access and display information.

Chapter 5 : "Syndication with RSS/Atom." This chapter deals with using Ajax together

with the data syndication formats RSS and Atom to create a web-based news aggregator.

Chapter 6 : "Web Services." This chapter brings web services into the Ajax picture.

Examples of how to call web services from the client are explained, as well as how to

create server-side proxies to work around browser security restrictions.

Chapter 7 : "JSON." This chapter introduces JavaScript Object Notation (JSON) as an

alternate data transmission format for Ajax communications. Advantages and

disadvantages over using XML and plain text are discussed.

Chapter 8 : "Web Site Widgets." This chapter brings the techniques from the previous

chapters into focus by creating Ajax widgets that can be included in your web site.

Chapter 9 : "AjaxMail." This chapter walks you through the development of a complete

web application, AjaxMail. This application is an Ajax-based e-mail system that uses many

of the techniques described earlier in the book.

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