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1820 professional javascript for web developers

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Professional JavaScript™ for Web Developers

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Professional JavaScript™ for Web Developers
Nicholas C. Zakas

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Professional JavaScript™ for Web Developers

Copyright © 2005 by Wiley Publishing Inc. All rights reserved.
Published by Wiley Publishing, Inc., Indianapolis, Indiana
Published simultaneously in Canada
No part of this publication may be reproduced, stored in a retrieval system, or transmitted in any form
or by any means, electronic, mechanical, photocopying, recording, scanning, or otherwise, except as
permitted under Section 107 or 108 of the 1976 United States Copyright Act, without either the prior
written permission of the Publisher, or authorization through payment of the appropriate per-copy fee
to the Copyright Clearance Center, Inc., 222 Rosewood Drive, Danvers, MA 01923, (978) 750-8400, fax
(978) 646-8700. Requests to the Publisher for permission should be addressed to the Legal Department,
Wiley Publishing, Inc., 10475 Crosspoint Blvd., Indianapolis, IN 46256, (317) 572-3447, fax (317)
572-4355, or online at www.wiley.com/go/permissions.
LIMIT OF LIABILITY/DISCLAIMER OF WARRANTY: THE PUBLISHER AND THE AUTHOR
MAKE NO REPRESENTATIONS OR WARRANTIES WITH RESPECT TO THE ACCURACY OR
COMPLETENESS OF THE CONTENTS OF THIS WORK AND SPECIFICALLY DISCLAIM ALL
WARRANTIES, INCLUDING WITHOUT LIMITATION WARRANTIES OF FITNESS FOR A PARTICULAR PURPOSE. NO WARRANTY MAY BE CREATED OR EXTENDED BY SALES OR PROMOTIONAL MATERIALS. THE ADVICE AND STRATEGIES CONTAINED HEREIN MAY NOT BE
SUITABLE FOR EVERY SITUATION. THIS WORK IS SOLD WITH THE UNDERSTANDING THAT
THE PUBLISHER IS NOT ENGAGED IN RENDERING LEGAL, ACCOUNTING, OR OTHER PROFESSIONAL SERVICES. IF PROFESSIONAL ASSISTANCE IS REQUIRED, THE SERVICES OF A
COMPETENT PROFESSIONAL PERSON SHOULD BE SOUGHT. NEITHER THE PUBLISHER NOT
THE AUTHOR SHALL BE LIABLE FOR DAMAGES ARISING HEREFROM. THE FACT THAT AN
ORGANIZATION OR WEBSITE IS REFERRED TO IN THIS WORK AS A CITATION AND/OR A
POTENTIAL SOURCE OF FURTHER INFORMATION DOES NOT MEAN THAT THE AUTHOR OR
THE PUBLISHER ENDORSES THE INFORMATION THE ORGANIZATION OR WEBSITE MAY
PROVIDE OR RECOMMENDATIONS IT MAY MAKE. FURTHER, READERS SHOULD BE AWARE
THAT INTERNET WEBSITES LISTED IN THIS WORK MAY HAVE CHANGED OR DISAPPEARED
BETWEEN WHEN THIS WORK WAS WRITTEN AND WHEN IT IS READ.
For general information on our other products and services please contact our Customer Care Department within the United States at (800) 762-2974, outside the United States at (317) 572-3993 or fax (317)
572-4002.
Trademarks: Wiley, the Wiley Publishing logo, Wrox, the Wrox logo, and Programmer to Programmer
are trademarks or registered trademarks of John Wiley & Sons, Inc. and/or its affiliates. JavaScript is a
trademark of Sun Microsystems, Inc. in the United States and other countries. All other trademarks are
the property of their respective owners. Wiley Publishing, Inc., is not associated with any product or
vendor mentioned in this book.
Wiley also publishes its books in a variety of electronic formats. Some content that appears in print
may not be available in electronic books.
Library of Congress Cataloging-in-Publication Data is available from the publisher.
ISBN-13: 978-0-7645-7908-0
ISBN-10: 0-7645-7908-8
Printed in the United States of America
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About the Author
Nicholas C. Zakas is a user interface designer for Web applications, specializing in client-side technologies such as JavaScript, HTML, and CSS. Nicholas currently works as Senior Software Engineer, Design
Engineering, at MatrixOne, Inc. located in Westford, Massachusetts, USA.
Nicholas has a B.S. in Computer Science from Merrimack College, where he learned traditional programming in C and C++. During college, he began investigating the World Wide Web and HTML in his
spare time, eventually teaching himself enough to be hired as Webmaster of a small software company
named Radnet, Inc. in Wakefield, Massachusetts, USA. It was there that Nicholas began learning
JavaScript and working on Web applications.
Nicholas can be reached through his Web site, http://www.nczonline.net/.

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Credits
Vice President and Executive Group Publisher:

Development Editor:

Richard Swadley

Sharon Nash

Vice President and Publisher:

Senior Production Editor:

Joseph B. Wikert

Angela Smith

Acquisitions Editor:

Technical Editor:

Jim Minatel

Jean-Luc David, Wiley-Dreamtech India Pvt Ltd

Editorial Manager:

Text Design & Composition:

Mary Beth Wakefield

Wiley Composition Services

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Acknowledgments
It takes more than just one person to write a book of this nature, despite the single name on the front
cover. Without the help of numerous individuals, this book would not have been possible.
First are foremost, thanks to everyone at Wiley Publishing, especially Jim Minatel and Sharon Nash, for
providing all the guidance and support that a new author needs.
Thanks to all those who offered their ideas on what a good JavaScript book should include: Keith
Ciociola, Ken Fearnley, John Rajan, and Douglas Swatski.
A special thanks to everyone who reviewed the subject matter ahead of time: Erik Arvidsson, Bradley
Baumann, Guilherme Blanco, Douglas Crockford, Jean-Luc David, Emil A. Eklund, Brett Fielder, Jeremy
McPeak, and Micha Schopman. All your input was excellent and made for a much better book.
Thanks to Drs. Ed and Frances Bernard for keeping me in tip-top health during the writing of this book
and the past few years.
Last, but certainly not least, thanks to my family, mom, dad, and Greg, and my extremely understanding
girlfriend, Emily. Your love and support helped take me from the proposal to the final published copy.

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Contents
Acknowledgments
Introduction

vii
xxi

Chapter 1: What Is JavaScript?
A Short History
JavaScript Implementations

1
1
3

ECMAScript
The Document Object Model (DOM)
The Browser Object Model (BOM)

Summary

3
6
9

9

Chapter 2: ECMAScript Basics

11

Syntax
Variables
Keywords
Reserved Words
Primitive and Reference Values
Primitive Types

11
12
15
15
15
16

The
The
The
The
The
The

typeof operator
Undefined type
Null type
Boolean type
Number type
String type

16
17
18
18
18
20

Conversions

21

Converting to a string
Converting to a number
Type Casting

22
23
24

Reference Types

25

The Object class
The Boolean class
The Number class

26
27
27

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Contents
The String class
The instanceof operator

29
32

Operators

33

Unary operators
Bitwise operators
Boolean operators
Multiplicative operators
Additive operators
Relational operators
Equality operators
Conditional operator
Assignment operators
Comma operator

33
37
43
46
47
49
50
52
52
53

Statements

53

The if statement
Iterative statements
Labeled statements
The break and continue statements
The with statement
The switch statement

53
54
56
56
58
58

Functions

59

No overloading
The arguments object
The Function class
Closures

61
62
63
65

Summary

66

Chapter 3: Object Basics

67

Object-Oriented Terminology

67

Requirements of object-oriented languages
Composition of an object

Working with Objects

68
68

68

Declaration and instantiation
Object references
Dereferencing objects
Early versus late binding

68
69
69
69

Types of Objects

70

Native objects
Built-in objects
Host objects

70
81
87

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Contents
Scope

88

Public, protected, and private
Static is not static
The this keyword

Defining Classes and Objects
Factory paradigm
Constructor paradigm
Prototype paradigm
Hybrid constructor/prototype paradigm
Dynamic prototype method
Hybrid factory paradigm
Which one to use?
A practical example

Modifying Objects

88
88
89

90
90
92
93
94
95
96
97
97

99

Creating a new method
Redefining an existing method
Very late binding

Summary

99
100
101

102

Chapter 4: Inheritance

103

Inheritance in Action
Implementing Inheritance

103
104

Methods of inheritance
A more practical example

105
111

Alternative Inheritance Paradigms
zInherit
xbObjects

115
116
120

Summary

124

Chapter 5: JavaScript in the Browser
JavaScript in HTML

125
125

The

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