Node.js入门指南

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"Node: Up and Running" 是一本由Tom Hughes-Croucher和Mike Wilson编写的关于Node.js的书籍，旨在帮助读者快速上手并掌握Node.js开发。在这本PDF电子书中，作者深入浅出地介绍了Node.js的核心概念和技术。Node.js是一个基于Chrome V8引擎的JavaScript运行环境，它以其非阻塞I/O模型和事件驱动的设计理念，使得JavaScript能够用于构建高性能的网络应用程序。以下是本书中可能涵盖的一些关键知识点： 1. **JavaScript基础**: 由于Node.js是用JavaScript编写的，因此理解JavaScript的基本语法和特性至关重要。书中可能涵盖了变量、数据类型、控制流语句、函数以及面向对象编程等基础知识。 2. **Node.js架构**: 书中可能详细讲解了Node.js如何利用单线程事件循环处理大量并发请求，以及V8引擎在提升性能方面的作用。 3. **模块系统**: Node.js有一个强大的模块系统，允许开发者将代码组织成可重用的模块。书中可能会介绍`require()`函数的使用，以及如何编写和发布自定义模块。 4. **文件系统操作**: Node.js提供了方便的API来与本地文件系统交互，如读写文件、目录操作等。这在构建服务器端应用时非常实用。 5. **网络编程**: 作为网络应用开发框架，Node.js支持HTTP、TCP、UDP等协议，可用于创建Web服务器、WebSocket服务等。书中会展示如何使用这些API创建和管理网络连接。 6. **异步编程**: 异步编程是Node.js的核心特性，通过回调函数、Promise或async/await处理异步任务，避免了传统回调地狱的问题。书中可能详细讨论了这些异步处理策略。 7. **中间件和路由**: 介绍Express.js等框架，它们提供了一种简洁的方式来组织Web应用的中间件和路由，使得开发更高效。 8. **性能优化**: 考虑到Node.js的高性能特性，书中可能涉及如何监测和优化应用程序的性能，如使用C++扩展、内存管理等。 9. **测试和调试**: 讲解如何使用Mocha、Chai等工具进行单元测试和集成测试，以及如何利用Node.js的内置调试器进行问题排查。 10. **社区和生态系统**: 介绍Node.js的开源生态，包括npm（Node Package Manager）中的各种工具和库，以及如何参与和贡献开源项目。这本书对于初学者和有一定经验的开发者都是很好的学习资源，它不仅讲解了Node.js的基础知识，还提供了实践项目以加深理解。通过学习，读者可以快速地开始使用Node.js开发高性能的网络应用。

To my friends, who have listened to my bitching (especially Yta, Emily, Eric, Gris,

Sarah, Allan, Harold and Daniella, and Hipster Ariel). To the countless people who

have given me encouragement, suggestions, and feedback. I couldn’t have done it

without you.

To the readers of this tome, thank you for trusting me with your learning.

xiv | Preface

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CHAPTER 1

A Very Brief Introduction to Node.js

Node.js is many things, but mostly it’s a way of running JavaScript outside the web

browser. This book will cover why that’s important and the benefits that Node.js pro-

vides. This introduction attempts to sum up that explanation in a few paragraphs,

rather than a few hundred pages.

Many people use the JavaScript programming language extensively for programming

the interfaces of websites. Node.js allows this popular programming language to be

applied in many more contexts, in particular on web servers. There are several notable

features about Node.js that make it worthy of interest.

Node is a wrapper around the high-performance V8 JavaScript runtime from the Google

Chrome browser. Node tunes V8 to work better in contexts other than the browser,

mostly by providing additional APIs that are optimized for specific use cases. For ex-

ample, in a server context, manipulation of binary data is often necessary. This is poorly

supported by the JavaScript language and, as a result, V8. Node’s Buffer class provides

easy manipulation of binary data. Thus, Node doesn’t just provide direct access to the

V8 JavaScript runtime. It also makes JavaScript more useful for the contexts in which

people use Node.

V8 itself uses some of the newest techniques in compiler technology. This often allows

code written in a high-level language such as JavaScript to perform similarly to code

written in a lower-level language, such as C, with a fraction of the development cost.

This focus on performance is a key aspect of Node.

JavaScript is an event-driven language, and Node uses this to its advantage to produce

highly scalable servers. Using an architecture called an event loop, Node makes pro-

gramming highly scalable servers both easy and safe. There are various strategies that

are used to make servers performant. Node has chosen an architecture that performs

very well but also reduces the complexity for the application developer. This is an

extremely important feature. Programming concurrency is hard and fraught with dan-

ger. Node sidesteps this challenge while still offering impressive performance. As al-

ways, any approach still has trade-offs, and these are discussed in detail later in the

book.

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To support the event-loop approach, Node supplies a set of “nonblocking” libraries.

In essence, these are interfaces to things such as the filesystem or databases, which

operate in an event-driven way. When you make a request to the filesystem, rather than

requiring Node to wait for the hard drive to spin up and retrieve the file, the nonblocking

interface simply notifies Node when it has access, in the same way that web browsers

notify your code about an onclick event. This model simplifies access to slow resources

in a scalable way that is intuitive to JavaScript programmers and easy to learn for ev-

eryone else.

Although not unique to Node, supporting JavaScript on the server is also a powerful

feature. Whether we like it or not, the browser environment gives us little choice of

programming languages. Certainly, JavaScript is the only choice if we would like our

code to work in any reasonable percentage of browsers. To achieve any aspirations of

sharing code between the server and the browser, we must use JavaScript. Due to the

increasing complexity of client applications that we are building in the browser using

JavaScript (such as Gmail), the more code we can share between the browser and the

server, the more we can reduce the cost of creating rich web applications. Because we

must rely on JavaScript in the browser, having a server-side environment that uses

JavaScript opens the door to code sharing in a way that is not possible with other server-

side languages, such as PHP, Java, Ruby, or Python. Although there are other platforms

that support programming web servers with JavaScript, Node is quickly becoming the

dominant platform in the space.

Aside from what you can build with Node, one extremely pleasing aspect is how much

you can build for Node. Node is extremely extensible, with a large volume of commu-

nity modules that have been built in the relatively short time since the project’s release.

Many of these are drivers to connect with databases or other software, but many are

also useful software applications in their own right.

The last reason to celebrate Node, but certainly not the least important, is its commu-

nity. The Node project is still very young, and yet rarely have we seen such fervor around

a project. Both novices and experts have coalesced around the project to use and con-

tribute to Node, making it both a pleasure to explore and a supportive place to share

and get advice.

Installing Node.js

Installing Node.js is extremely simple. Node runs on Windows, Linux, Mac, and other

POSIX OSes (such as Solaris and BSD). Node.js is available from two primary locations:

the project’s website or the GitHub repository. You’re probably better off with the

Node website because it contains the stable releases. The latest cutting-edge features

are hosted on GitHub for the core development team and anyone else who wants a

copy. Although these features are new and often intriguing, they are also less reliable

than those in a stable release.

4 | Chapter 1: A Very Brief Introduction to Node.js

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