JavaScript面向对象设计原则详解：尼古拉斯·扎卡斯著作

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《面向对象的JavaScript设计原则》是由尼古拉斯·Z·扎卡斯(Nicholas C. Zakas)所著的一本深入讲解JavaScript面向对象编程(OOP)实践的书籍。这本书在2014年首次出版，版权受保护，未经版权所有者和出版商事先书面许可，禁止任何形式的复制或传输，包括但不限于复印、录音以及通过任何信息存储和检索系统。该书的核心内容围绕着JavaScript面向对象设计的七大原则展开，这些原则旨在帮助开发者编写出可维护、可扩展和模块化的代码。以下是部分内容的概述： 1. 单一职责原则（Single Responsibility Principle, SRP）: 一个类或对象应仅负责一个单一的功能或责任，确保其关注点清晰，易于测试和理解。 2. 开放封闭原则（Open-Closed Principle, OCP）: 类的行为可以修改，但其结构不应被修改。这意味着可以通过扩展已有类的方式增加新功能，而无需修改原始类。 3. 里氏替换原则（Liskov Substitution Principle, LSP）: 子类应该能够替换掉它们的基类而不会影响程序的正确性。这强调了继承的正确使用和多态的重要性。 4. 接口隔离原则（Interface Segregation Principle, ISP）: 降低接口的复杂性，只暴露那些客户真正需要的方法，避免强迫使用者依赖他们不需要的接口。 5. 依赖倒置原则（Dependency Inversion Principle, DIP）: 高层模块不应该依赖于底层模块，两者都应该依赖于抽象。这有助于创建松耦合的系统。 6. 迪米特法则（Law of Demeter, LOD）: 减少对象间的耦合，每个对象应该只与自己的朋友通信，而不是随意与其他对象交互，提高代码的可测试性和可维护性。 7. 组合/聚合优于继承（Composition/Aggregation over Inheritance, CAOI）: 在设计时优先考虑组合而非继承，因为组合更灵活且有利于代码的复用和扩展。《面向对象的JavaScript设计原则》不仅提供了理论指导，还通过实际示例和最佳实践，帮助读者掌握如何在JavaScript项目中有效地应用这些原则，提升代码质量，使软件设计更加模块化和易于维护。对于希望深入理解并运用面向对象编程思想的JavaScript开发者来说，这是一本不可多得的参考书。

acknowledgmenTs

I’d like to thank Kate Matsudaira for convincing me that self-publishing

an ebook was the best way to get this information out. Without her advice,

I’d probably still be trying to ﬁgure out what I should do with the infor-

mation contained in this book.

Thanks to Rob Friesel for once again providing excellent feedback on

an early copy of this book, and Cody Lindley for his suggestions. Additional

thanks to Angus Croll for his technical review of the ﬁnished version—

his nitpicking made this book much better.

Thanks as well to Bill Pollock, whom I met at a conference and who

started the ball rolling on publishing this book.

www.it-ebooks.info

xviii Introduction

Aggregation One object can reference another object.

Inheritance A newly created object has the same characteristics

as another object without explicitly duplicating its functionality.

Polymorphism One interface may be implemented by multiple

objects.

JavaScript has all these characteristics, though because the language

has no concept of classes, some aren’t implemented in quite the way you

might expect. At ﬁrst glance, a JavaScript program might even look like

a procedural program you would write in C. If you can write a function

and pass it some variables, you have a working script that seemingly has

no objects. A closer look at the language, however, reveals the existence

of objects through the use of dot notation.

Many object-oriented languages use dot notation to access properties

and methods on objects, and JavaScript is syntactically the same. But in

JavaScript, you never need to write a class deﬁnition, import a package,

or include a header ﬁle. You just start coding with the data types that you

want, and you can group those together in any number of ways. You could

certainly write JavaScript in a procedural way, but its true power emerges

when you take advantage of its object-oriented nature. That’s what this

book is about.

Make no mistake: A lot of the concepts you may have learned in

more traditional object-oriented programming languages don’t neces-

sarily apply to JavaScript. While that often confuses beginners, as you

read, you’ll quickly ﬁnd that JavaScript’s weakly typed nature allows

you to write less code to accomplish the same tasks as other languages.

You can just start coding without planning the classes that you need

ahead of time. Need an object with speciﬁc ﬁelds? Just create an ad hoc

object wherever you want. Did you forget to add a method to that object?

No problem—just add it later.

Inside these pages, you’ll learn the unique way that JavaScript

approaches object-oriented programming. Leave behind the notions

of classes and class-based inheritance and learn about prototype-based

inheritance and constructor functions that behave similarly. You’ll learn

how to create objects, deﬁne your own types, use inheritance, and other-

wise manipulate objects to get the most out of them. In short, you’ll learn

everything you need to know to understand and write JavaScript profes-

sionally. Enjoy!

Who This Book Is For

This book is intended as a guide for those who already understand object-

oriented programming but want to know exactly how the concept works in

JavaScript. Familiarity with Java, C#, or object-oriented programming in

www.it-ebooks.info

Introduction xix

other languages is a strong indicator that this book is for you. In particu-

lar, this book is aimed at three groups of readers:

• Developers who are familiar with object-oriented programming con-

cepts and want to apply them to JavaScript

• Web application and Node.js developers trying to structure their code

more effectively

• Novice JavaScript developers trying to gain a deeper understanding

of the language

This book is not for beginners who have never written JavaScript. You

will need a good understanding of how to write and execute JavaScript

code to follow along.

Overview

Chapter 1: Primitive and Reference Types introduces the two different

value types in JavaScript: primitive and reference. You’ll learn what distin-

guishes them from each other and how understanding their differences

is important to an overall understanding of JavaScript.

Chapter 2: Functions explains the ins and outs of functions in

JavaScript. First-class functions are what makes JavaScript such an inter-

esting language.

Chapter 3: Understanding Objects details the makeup of objects in

JavaScript. JavaScript objects behave differently than objects in other lan-

guages, so a deep understanding of how objects work is vital to mastering

the language.

Chapter 4: Constructors and Prototypes expands on the previous

discussion of functions by looking more speciﬁcally at constructors. All

constructors are functions, but they are used a little bit differently. This

chapter explores the differences while also talking about creating your

own custom types.

Chapter 5: Inheritance explains how inheritance is accomplished

in JavaScript. Though there are no classes in JavaScript, that doesn’t

mean inheritance isn’t possible. In this chapter, you’ll learn about proto-

typal inheritance and how it differs from class-based inheritance.

Chapter 6: Object Patterns walks through common object pat-

terns. There are many different ways to build and compose objects in

JavaScript, and this chapter introduces you to the most popular patterns

for doing so.

Help and Support

If you have questions, comments, or other feedback about this book,

please visit the mailing list at http://groups.google.com/group/zakasbooks.

www.it-ebooks.info

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