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JavaScript: The Good Parts

Douglas Crockford

Beijing • Cambridge • Farnham • Köln • Sebastopol • Taipei • Tokyo

JavaScript: The Good Parts
by Douglas Crockford
Copyright © 2008 Yahoo! Inc. All rights reserved. Printed in the United States of America. Published by O’Reilly Media, Inc., 1005 Gravenstein Highway North, Sebastopol, CA 95472. O’Reilly books may bepurchased for educational, business, or sales promotional use. Online editions are also available for most titles (safari.oreilly.com). For more information, contact our corporate/institutional sales department: (800) 998-9938 or corporate@oreilly.com.

Editor: Simon St.Laurent Production Editor: Sumita Mukherji Copyeditor: Genevieve d’Entremont Proofreader: Sumita Mukherji Printing History:
May2008: First Edition.

Indexer: Julie Hawks Cover Designer: Karen Montgomery Interior Designer: David Futato Illustrator: Robert Romano

Nutshell Handbook, the Nutshell Handbook logo, and the O’Reilly logo are registered trademarks of O’Reilly Media, Inc. JavaScript: The Good Parts, the image of a Plain Tiger butterfly, and related trade dress are trademarks of O’Reilly Media, Inc. Java™ is atrademark of Sun Microsystems, Inc. Many of the designations used by manufacturers and sellers to distinguish their products are claimed as trademarks. Where those designations appear in this book, and O’Reilly Media, Inc. was aware of a trademark claim, the designations have been printed in caps or initial caps. While every precaution has been taken in the preparation of this book, the publisherand author assume no responsibility for errors or omissions, or for damages resulting from the use of the information contained herein.

This book uses RepKover™ a durable and flexible lay-flat binding. , ISBN: 978-0-596-51774-8 [M]

[7/08]

For the Lads: Clement, Philbert, Seymore, Stern, and, lest we forget, C. Twildo.

Table of Contents

Preface . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xi 1. Good Parts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Why JavaScript? Analyzing JavaScript A Simple Testing Ground 2 3 4

2. Grammar . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . 5
Whitespace Names Numbers Strings Statements Expressions Literals Functions 5 6 7 8 10 15 17 19

3. Objects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
Object Literals Retrieval Update Reference Prototype Reflection Enumeration Delete Global Abatement 20 21 22 22 22 23 24 24 25

vii

4....