Reliable JavaScript E-Book

Lawrence Spencer

• Herausgeber: John Wiley & Sons
• Kategorie: Wissenschaft und neue Technologien
• Sprache: Englisch
• Veröffentlichungsjahr: 2015

Seitenzahl: 603

Beschreibung

Create more robust applications with a test-first approach to JavaScript Reliable JavaScript, How to Code Safely in the World's Most Dangerous Language demonstrates how to create test-driven development for large-scale JavaScript applications that will stand the test of time and stay accurate through long-term use and maintenance. Taking a test-first approach to software architecture, this book walks you through several patterns and practices and explains what they are supposed to do by having you write unit tests. Write the code to pass the unit tests, so you not only develop your technique for structuring large-scale applications, but you also learn how to test your work. You'll come away with hands-on practice that results in code that is correct from the start, and has the test coverage to ensure that it stays correct during subsequent maintenance. All code is provided both in the text and on the web, so you can immediately get started designing more complete, robust applications. JavaScript has graduated from field-validation scripts to full-scale applications, but many developers still approach their work as if they were writing simple scripts. If you're one of those developers, this book is the solution you need to whip your code into shape and create JavaScript applications that work. * Write more concise and elegant code by thinking in JavaScript * Test the implementation and use of common design patterns * Master the use of advanced JavaScript features * Ensure your code's conformance to your organization's standards If you're ready to step up your code and develop more complete software solutions, Reliable JavaScript is your essential resource.

Leseprobe

Reliable JavaScript®

Lawrence D. Spencer Seth H. Richards

Reliable JavaScript®

Published by John Wiley & Sons, Inc. 10475 Crosspoint Boulevard Indianapolis, IN 46256 www.wiley.com

Copyright © 2015 by John Wiley & Sons, Inc., Indianapolis, Indiana

Published simultaneously in Canada

ISBN: 978-1-119-02872-7

ISBN: 978-1-119-02873-4 (ebk)

ISBN: 978-1-119-02874-1 (ebk)

Manufactured in the United States of America

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For general information on our other products and services please contact our Customer Care Department within the United States at [phone], outside the United States at [phone] or fax [phone].

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Library of Congress Control Number: 2015941920

Trademarks: Wiley, the Wiley logo, Wrox, the Wrox logo, Programmer to Programmer, and related trade dress are trademarks or registered trademarks of John Wiley & Sons, Inc. and/or its affiliates, in the United States and other countries, and may not be used without written permission. JavaScript is a registered trademark of Oracle America, Inc. All other trademarks are the property of their respective owners. John Wiley & Sons, Inc. is not associated with any product or vendor mentioned in this book.

We dedicate this book to all JavaScript developers who work hard to hone their craft. You are making the world a more beautiful place.

CREDITS

PROJECT EDITORChristina Haviland

TECHNICAL EDITORSKeith Pepin John Peloquin

PRODUCTION MANAGERKathleen Wisor

COPY EDITORNancy Rapoport

MANAGER OF CONTENT DEVELOPMENT & ASSEMBLYMary Beth Wakefield

MARKETING DIRECTORDavid Mayhew

MARKETING MANAGERCarrie Sherrill

PROFESSIONAL TECHNOLOGY & STRATEGY DIRECTORBarry Pruett

BUSINESS MANAGERAmy Knies

ASSOCIATE PUBLISHERJim Minatel

PROJECT COORDINATOR, COVERBrent Savage

PROOFREADERNancy Carrasco

INDEXERJohnna VanHoose Dinse

COVER DESIGNERWiley

COVER IMAGE© Getty Images/Andrew Rich

ABOUT THE AUTHORS

LARRY SPENCER is Vice President of Application Development at ScerIS, a software and services company in Sudbury, Massachusetts. He and his team create browser-based applications in AngularJS, with a C#/Web API/SQL Server back end. Larry's 35-year career has included stints programming in COBOL, C, C++, C#, and even mainframe assembly language, but he says JavaScript is the most fun. A frequent speaker at Code Camps and other gatherings, Larry enjoys sharing his love of software with the development community. You can find his blog at http://FascinatedWithSoftware.com.

Larry's outside interests include philosophy, chess, and classical guitar. He lives in Marlborough, Massachusetts.

SETH RICHARDS has been crafting software professionally since 2002. He got his start programming embedded devices for the bar and nightclub industry and transitioned to web application development in 2007. He has worked on numerous web-based applications ranging from an enterprise-class geographic information system–centric physical asset management system to a social network for product discovery and recommendation.

Seth graduated from Plymouth State College (now University) in Plymouth, New Hampshire, where he studied computer science and mathematics. He is currently pursuing his M.S. in Computer Science from the Georgia Institute of Technology. Seth's blog can be found at http://blog.shrichards.com, and he can be followed on Twitter at @shrichards.

ABOUT THE TECHNICAL EDITORS

KEITH PEPIN has been developing sites and applications on the web for over 17 years. Early in his career, he fell in love with JavaScript and has been passionately building dynamic user experiences ever since. He is currently a Senior Software Engineer at Meltwater, and is using HTML5, CSS3, JavaScript, AngularJS, Node.js, and MongoDB to build the next generation of their online marketing intelligence platform. When not coding or spending time with his family, he enjoys other geeky pursuits, including all forms of games, comic books, painting, and sketching.

JOHN PELOQUIN is a software engineer with over 10 years of JavaScript experience ranging across applications of all sizes. John earned his B.A. in Mathematics from U.C. Berkeley and is currently a lead engineer at Spreemo, a healthcare technology startup in NYC. Prior to editing this volume, John edited Professional Website Performance by Peter Smith (Wiley 2012) and Professional JavaScript for Web Developers, 3rd ed. by Nicholas Zakas (Wiley 2012). When he is not coding or collecting errata, John can occasionally be found doing stand-up comedy at an open mic.

ACKNOWLEDGMENTS

Thank you to my wife, Bethany, for her love and support while we wrote this book, and for enduring (or enjoying?) many husband-less nights and weekends while I worked to meet a deadline.

–SETH RICHARDS

Thanks to my family for encouraging me to pursue my dreams. My dreams may include writing a book, but they begin and end with you.

–LARRY SPENCER

This book would not have been possible without the willingness of others to share their knowledge and expertise with us and the community at large in book, blog, and source-code format. Together, we'd like to acknowledge and thank:

Douglas Crockford, for his exposure of good parts of JavaScript and his work on jsLint.

Nicolas Zakas, for the numerous books and blog posts he wrote that acted as guides through JavaScript's sometimes-treacherous waters, and also his maintenance of and contributions to ESLint.

Stoyan Stefanov, for his instruction on applying pattern-based development to JavaScript.

Robert C. Martin, for instilling in us the desire to write clean code.

Fredrik Appelberg, for his creation of, and Dave Clayton for his contributions to, the AOP.js aspect-oriented programming framework.

Mike Bostock, for inspiring us with the D3 library for SVG graphics.

The folks at Pivotal Labs, for the creation of the open-source JavaScript framework Jasmine, and members of the community that have contributed to the framework.

The AngularJS team, for showing the world a great way to build single-page applications.

The vast and growing network of generous people on sites such as Stack Overflow and GitHub. Without you, we'd still be thumbing through manuals.

We would also like to express our appreciation to our project editor, Chris Haviland, who deftly maneuvered us through the writing process from beginning to end. Our copy editor, Nancy Rapoport, has read our book more carefully, and more times, than anyone else ever will. For her dedication and suggestions we offer heartfelt thanks. We would also like to express our sincerest thanks to our technical editors, Keith Pepin and John Peloquin. Their JavaScript prowess helped us avoid more than a few technical errors. Should any errors still exist, it's likely because we didn't follow some of their advice. Our hats are off to you, gentlemen.

Finally, we'd like to thank Carol Long, the Executive Acquisitions Editor at Wiley, who gave us the opportunity to write this book. Without her, we'd still just be a couple of guys that write software for a living. We're still that, but now we're authors, too. Carol announced her retirement from the publishing industry just before we finished the book. We sure hope we weren't the straw that broke the camel's back! Thank you, Carol, and we wish you nothing but sunny days and margaritas in your retirement.

–LARRY AND SETH

CONTENTS

INTRODUCTION

THE RISE OF JAVASCRIPT AS A FIRST-CLASS LANGUAGE

THE EASE OF WRITING TRULY DISASTROUS CODE IN JAVASCRIPT

THE EASE OF UNINTENTIONALLY BREAKING JAVASCRIPT CODE

THIS BOOK'S INTENDED AUDIENCE

HOW THIS BOOK IS STRUCTURED

WHAT YOU NEED TO USE THIS BOOK

CONVENTIONS

SOURCE CODE

ERRATA

P2P.WROX.COM

PART I: LAYING A SOLID FOUNDATION

CHAPTER 1 PRACTICING SKILLFUL SOFTWARE ENGINEERING

WRITING CODE THAT STARTS CORRECT

WRITING CODE THAT STAYS CORRECT

SUMMARY

CHAPTER 2 TOOLING UP

USING A TESTING FRAMEWORK

USING A DEPENDENCY-INJECTION FRAMEWORK

USING AN ASPECT TOOLKIT

USING A CODE-CHECKING TOOL

SUMMARY

CHAPTER 3 CONSTRUCTING RELIABLE OBJECTS

USING PRIMITIVES

USING OBJECT LITERALS

USING THE MODULE PATTERN

USING OBJECT PROTOTYPES AND PROTOTYPAL INHERITANCE

CREATING OBJECTS WITH NEW

USING CLASSICAL INHERITANCE

USING FUNCTIONAL INHERITANCE

MONKEY-PATCHING

SUMMARY

PART II: TESTING PATTERN-BASED CODE

CHAPTER 4 REVIEWING THE BENEFITS OF PATTERNS

CASE STUDY

PRODUCING MORE ELEGANT CODE BY USING A BROADER VOCABULARY

PRODUCING RELIABLE CODE WITH WELL-ENGINEERED, WELL-TESTED BUILDING BLOCKS

SUMMARY

CHAPTER 5 ENSURING CORRECT USE OF THE CALLBACK PATTERN

UNDERSTANDING THE PATTERN THROUGH UNIT TESTS

AVOIDING PROBLEMS

SUMMARY

CHAPTER 6 ENSURING CORRECT USE OF THE PROMISE PATTERN

UNDERSTANDING PROMISES THROUGH UNIT TESTS

CHAINING PROMISES

USING A PROMISE WRAPPER

UNDERSTANDING STATES AND FATES

DISTINGUISHING STANDARD PROMISES FROM JQUERY PROMISES

SUMMARY

CHAPTER 7 ENSURING CORRECT USE OF PARTIAL FUNCTION APPLICATION

UNIT-TESTING A PARTIAL FUNCTION APPLICATION

CREATING AN ASPECT FOR PARTIAL FUNCTION APPLICATION

DISTINGUISHING BETWEEN PARTIAL FUNCTION APPLICATION AND CURRYING

SUMMARY

CHAPTER 8 ENSURING CORRECT USE OF THE MEMOIZATION PATTERN

UNDERSTANDING THE PATTERN THROUGH UNIT TESTS

ADDING MEMOIZATION WITH AOP

SUMMARY

CHAPTER 9 ENSURING CORRECT IMPLEMENTATION OF THE SINGLETON PATTERN

UNDERSTANDING THE PATTERN THROUGH UNIT TESTS

SUMMARY

CHAPTER 10 ENSURING CORRECT IMPLEMENTATION OF THE FACTORY PATTERN

WRITING UNIT TESTS FOR A FACTORY

IMPLEMENTING THE FACTORY PATTERN

CONSIDERING OTHER FACTORY TYPES

SUMMARY

CHAPTER 11 ENSURING CORRECT IMPLEMENTATION AND USE OF THE SANDBOX PATTERN

UNDERSTANDING THE PATTERN THROUGH UNIT TESTS

SUMMARY

CHAPTER 12 ENSURING CORRECT IMPLEMENTATION OF THE DECORATOR PATTERN

DEVELOPING A DECORATOR THE TEST-DRIVEN WAY

SUMMARY

CHAPTER 13 ENSURING CORRECT IMPLEMENTATION OF THE STRATEGY PATTERN

UNDERSTANDING THE PATTERN THROUGH UNIT TESTS

SUMMARY

CHAPTER 14 ENSURING CORRECT IMPLEMENTATION OF THE PROXY PATTERN

DEVELOPING A PROXY THE TEST-DRIVEN WAY

SUMMARY

CHAPTER 15 ENSURING CORRECT IMPLEMENTATION OF CHAINABLE METHODS

UNDERSTANDING THE PATTERN THROUGH UNIT TESTS

CHAINING THEN

SUMMARY

PART III: TESTING AND WRITING WITH ADVANCED JAVASCRIPT FEATURES

CHAPTER 16 CONFORMING TO INTERFACES IN AN INTERFACE-FREE LANGUAGE

UNDERSTANDING THE BENEFITS OF INTERFACES

UNDERSTANDING THE INTERFACE SEGREGATION PRINCIPLE

USING TEST-DRIVEN DEVELOPMENT TO CREATE A CONTRACT REGISTRY

SUMMARY:

CHAPTER 17 ENSURING CORRECT ARGUMENT TYPES

UNDERSTANDING THE OPPORTUNITIES AND RISKS POSED BY JAVASCRIPT’S TYPE-FREE PARAMETERS

EXTENDING THE CONTRACTREGISTRY TO CHECK ARGUMENTS

SUPPORTING CONTRACT LIBRARIES

PUTTING IT ALL TOGETHER

COMPARING THE ASPECT-ORIENTED SOLUTION TO A STATIC SOLUTION

SUMMARY

CHAPTER 18 ENSURING CORRECT USE OF CALL, APPLY, AND BIND

EXPLORING HOW THIS IS BOUND

CREATING AND TESTING CODE THAT USES CALL, APPLY, AND BIND

SUMMARY

CHAPTER 19 ENSURING CORRECT USE OF METHOD-BORROWING

ENSURING THE BORROWING OBJECT IS SUITABLE

ANTICIPATING SIDE EFFECTS ON THE BORROWER

ANTICIPATING SIDE EFFECTS ON THE DONOR OBJECT

SUMMARY

CHAPTER 20 ENSURING CORRECT USE OF MIXINS

CREATING AND USING MIXINS

SUMMARY

CHAPTER 21 TESTING ADVANCED PROGRAM ARCHITECTURES

ENSURING RELIABLE USE OF THE OBSERVER PATTERN

ENSURING RELIABLE USE OF THE MEDIATOR PATTERN

SUMMARY

PART IV: SPECIAL SUBJECTS IN TESTING

CHAPTER 22 TESTING DOM ACCESS

UNIT-TESTING UI

OPTIMIZING YOUR CODE WITH A PROFILER

SUMMARY

CHAPTER 23 ENSURING CONFORMANCE TO STANDARDS

USING ESLINT

ENFORCING ARCHITECTURAL DIVISIONS

SUMMARY

PART V: SUMMARY

CHAPTER 24 SUMMARY OF THE PRINCIPLES OF TEST-DRIVEN DEVELOPMENT

RECALLING WHY TEST-DRIVEN DEVELOPMENT IS WORTHWHILE

PRACTICING TEST-DRIVEN DEVELOPMENT

SUMMARY

CHAPTER 25 SUMMARY OF JAVASCRIPT IDIOMS IN THIS BOOK

REVIEWING OBJECTS

REVIEWING VARIABLES

REVIEWING FUNCTIONS

REVIEWING BOOLEAN OPERATIONS

SUMMARY

INDEX

EULA

List of Tables

Chapter 3

Table 3.1

Table 3.2

Table 3.3

Table 3.4

Table 3.5

Table 3.6

Table 3.7

Chapter 4

Table 4.1

Chapter 10

Table 10.1

Chapter 21

Table 21.1

Table 21.2

List of Illustrations

Chapter 1

Figure 1.1

Figure 1.2

Figure 1.3

Figure 1.4

Chapter 2

Figure 2.1

Figure 2.2

Figure 2.3

Figure 2.4

Figure 2.5

Figure 2.6

Figure 2.7

Figure 2.8

Figure 2.9

Figure 2.10

Figure 2.11

Figure 2.12

Figure 2.13

Chapter 3

Figure 3.1

Figure 3.2

Figure 3.3

Chapter 5

Figure 5.1

Figure 5.2

Figure 5.3

Figure 5.4

Figure 5.5

Figure 5.6

Figure 5.7

Figure 5.8

Chapter 6

Figure 6.1

Chapter 7

Figure 7.1

Chapter 8

Figure 8.1

Figure 8.2

Chapter 9

Figure 9.1

Figure 9.2

Figure 9.3

Figure 9.4

Chapter 10

Figure 10.1

Chapter 11

Figure 11.1

Figure 11.2

Figure 11.3

Figure 11.4

Figure 11.5

Figure 11.6

Figure 11.7

Figure 11.8

Figure 11.9

Chapter 12

Figure 12.1

Figure 12.2

Figure 12.3

Figure 12.4

Figure 12.5

Figure 12.6

Figure 12.7

Chapter 13

Figure 13.1

Figure 13.2

Figure 13.3

Figure 13.4

Chapter 14

Figure 14.1

Figure 14.2

Figure 14.3

Figure 14.4

Figure 14.5

Figure 14.6

Figure 14.7

Figure 14.8

Figure 14.9

Figure 14.10

Figure 14.11

Chapter 15

Figure 15.1

Figure 15.2

Figure 15.3

Figure 15.4

Figure 15.5

Figure 15.6

Chapter 16

Figure 16.1

Figure 16.2

Figure 16.3

Figure 16.4

Figure 16.5

Chapter 17

Figure 17.1

Figure 17.2

Chapter 18

Figure 18.1

Figure 18.2

Figure 18.3

Figure 18.4

Figure 18.5

Figure 18.6

Figure 18.7

Figure 18.8

Figure 18.9

Figure 18.10

Figure 18.11

Figure 18.12

Figure 18.13

Figure 18.14

Figure 18.15

Chapter 19

Figure 19.1

Figure 19.2

Figure 19.3

Figure 19.4

Figure 19.5

Figure 19.6

Figure 19.7

Chapter 20

Figure 20.1

Figure 20.2

Figure 20.3

Figure 20.4

Figure 20.5

Figure 20.6

Figure 20.7

Figure 20.8

Figure 20.9

Figure 20.10

Figure 20.11

Figure 20.12

Figure 20.13

Figure 20.14

Figure 20.15

Figure 20.16

Figure 20.17

Figure 20.18

Figure 20.19

Figure 20.20

Chapter 21

Figure 21.1

Figure 21.2

Figure 21.3

Figure 21.4

Figure 21.5

Figure 21.6

Chapter 22

Figure 22.1

Figure 22.2

Figure 22.3

Figure 22.4

Figure 22.5

Figure 22.6

Figure 22.7

Figure 22.8

Figure 22.9

Figure 22.10

Figure 22.11

Figure 22.12

Figure 22.13

Figure 22.14

Figure 22.15

Chapter 23

Figure 23.1

Figure 23.2

Figure 23.3

Figure 23.4

Figure 23.5

Figure 23.6

Figure 23.7

Figure 23.8

Figure 23.9

Figure 23.10

Figure 23.11

Figure 23.12

Figure 23.13

Figure 23.14

Figure 23.15

Figure 23.16

Guide

Cover

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INTRODUCTION

WHEN WE SHARED THE TITLE OF THIS BOOK, Reliable JavaScript, with fellow developers, we received feedback such as:

“Now

there's

a juxtaposition!”

“It must be a very short book.”

“Will I find it next to the latest John Grisham thriller in the fiction section of the bookstore?”

No, this book is not a work of fiction.

The feedback we received about the title of the book illustrates a broader perception about JavaScript that some developers with experience in classical, compiled languages have: JavaScript is used to create flashy portfolio websites or simple to-do apps; it has no business in my mission-critical enterprise application.

In the past that was true, but no more.

THE RISE OF JAVASCRIPT AS A FIRST-CLASS LANGUAGE

JavaScript's reputation as a wild child is well-deserved, and we hope to amuse you with some of its exploits in the next two sections. However, like a spoiled heiress who inherits the family business and surprises everyone by rising to the challenge, she has turned serious and responsible, lately showing herself capable of true greatness.

Her early life was as a dilettante, rarely entrusted with anything more than short “scripting” tasks. The decisions she made were simple: If a required field was not filled in, she should color it red; if a button was clicked, she should bring another page into view. Although her responsibilities were limited, she was easy to get along with and made many friends. To this day, most programmers' experience of her is primarily of this sort.

Then, in the shift that was to redefine her life, the world turned to the web. This had been her playground, her little place to amuse herself while members of The Old Boys Club did the real work on the server.

The wave started to break in the late 1990s when Microsoft introduced first iframes and then XMLHTTP. When Google made Ajax part of its Gmail application in 2004 and Google Maps in 2005, the wave came crashing down. The world was suddenly aware of just how much richer the web experience could be when the browser was entrusted with more than just displaying whatever the server dispensed.