精通Node.js：正确之道

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"Node.js the Right Way 是一本专为想要深入学习Node.js开发的读者准备的指南，旨在逐步引领读者成为Node.js专家。本书受到行业内专业人士的高度评价，认为它超越了JavaScript和Node.js的基础，深入讲解如何构建高质量的服务器端应用程序。" 在"Node.js the Right Way"中，作者不仅关注基础的JavaScript机制和Node.js的基本用法，还着重介绍了如何打造健壮、高效的服务器端应用。书中的内容涵盖了Node.js的灵活性和强大功能，特别适合已具备JavaScript基础并希望扩展到服务器基础设施领域的开发者。不同于其他入门书籍，"Node.js the Right Way"跳过了通常的"Hello World"示例，直接提供实用的例子，让读者能够快速理解Node.js的实际应用。这本书由知名专家和作者推荐，被认为是学习Node.js的首选资料，尤其对于那些对构建大规模应用感兴趣的开发者来说，它不仅仅是一个面向潮流的轻量级Web服务器框架的介绍。通过阅读本书，你可以期待学习到以下关键知识点： 1. **Node.js基础**：理解事件驱动的非阻塞I/O模型，以及V8引擎如何为Node.js提供高性能。 2. **模块系统**：掌握Node.js的内置模块，以及如何使用npm（Node Package Manager）安装和管理第三方模块。 3. **网络编程**：创建HTTP服务器，处理请求和响应，构建RESTful API。 4. **文件系统操作**：学习读写文件、目录管理和流操作。 5. **异步编程**：深入理解回调函数、Promise和async/await，有效避免回调地狱。 6. **错误处理**：学习如何优雅地处理和报告错误，确保代码的健壮性。 7. **性能优化**：了解如何进行性能监控和调试，以及如何优化代码和服务器配置。 8. **测试**：学习使用Mocha、Chai等工具编写单元测试和集成测试，确保代码质量。 9. **安全实践**：理解常见的安全问题，如XSS、CSRF等，并学习相应的防护策略。 10. **部署与维护**：了解如何在生产环境中部署Node.js应用，包括负载均衡、日志管理和故障恢复。通过这些深入的章节，读者将能够系统地掌握Node.js开发的各个方面，从而能够在实际项目中运用所学知识，构建出高效、稳定的服务器端应用。这本书是通往Node.js专家之路的重要一步，对于任何想要在Node.js领域提升自己的开发者来说，都是不可或缺的参考资料。

East of the mountain range, we find the client-side programs. These include

GUI tools of all stripes, consumer applications, mobile apps, and web apps.

Client-side programs interact directly with human beings, often by waiting

patiently for their input.

West of the mountains are the server-side programs. This vast expanse is

Node.js territory.

Deep within the server-side region lies the Web—that old guard of HTTP, Ajax,

REST, and JSON. The websites, apps, and APIs that consume so much of

our collective mental energy live here.

Because we spend so much time thinking about the Web, we overemphasize

Node’s use in developing web applications. People ask, “How is Node better

for making web apps?” or, “How can I make a REST service with Node?”

These are good questions, but they miss the point. Node is great for a wider

range of things, and this book explores that larger world.

Node’s Niche

Since JavaScript’s first appearance in 1995, it has been solving problems all

along the front-end/back-end spectrum. The following figure shows this

spectrum and where Node.js fits within it.

Figure 2—Node’s place in the JavaScript spectrum

In the web browser on the right, much of the scripting involves waiting for

user interaction. Click here, drag that, choose a file, etc. JavaScript has been

extraordinarily successful in this space.

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As long as there’s something left to do, Node’s event loop will keep spinning.

Whenever an event occurs, Node invokes any callbacks (event handlers) that

are listening for that event.

As a Node developer, your job is to create the callback functions that get

executed in response to events. Any number of callbacks can respond to any

event, but only one callback function will ever be executing at any time.

Everything else your program might do—like waiting for data from a file or

an incoming HTTP request—is handled by Node, in parallel, behind the scenes.

Your application code will never be executed at the same time as anything

else. It will always have the full attention of Node’s JavaScript engine while

it’s running.

Single-Threaded and Highly Parallel

Other systems try to gain parallelism by running lots of code at the same

time, typically by spawning many threads. But not Node.js. For JavaScript,

Node is a single-threaded environment. At most, only one line of your code

will ever be executing at any time.

Node gets away with this by doing most I/O tasks using nonblocking

techniques. Rather than waiting line-by-line for an operation to finish, you

create a callback function that will be invoked when the operation eventually

succeeds or fails.

Your code should do what it needs to do, then quickly hand control back over

to the event loop so Node can work on something else. We’ll develop practical

examples of this throughout the book, starting in Chapter 2, Wrangling the

File System, on page 9.

If it seems strange to you that Node achieves parallelism by running only one

piece of code at a time, that’s because it is. It’s an example of something I call

a backwardism.

Backwardisms in Node.js

A backwardism is a concept that’s so bizarre that at first it seems completely

backwards. You’ve probably experienced many backwardisms while learning

to program, whether you noticed them or not.

Take the concept of a variable. In algebra it’s common to see equations like

“

7x + 3 = 24

.” Here,

is called a variable; it has exactly one value, and your job

is to figure out what that value is.

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Then when you start learning how to program, you quickly run into statements

like “

x = x + 7

.” Now

is still called a variable, but it can have any value that

you assign to it. It can even have different values at different times.

From algebra’s perspective, this is a backwardism. The equation “

x = x + 7

”

makes no sense at all. The notion of a variable in programming is not just a

little different—it’s 100 percent backwards. But once you understand the

concept of assignment, the programming variable makes perfect sense.

So it is with Node’s single-threaded event loop. From a multithreaded perspec-

tive, running just one piece of code at a time seems silly. But once you

understand event-driven programming—with nonblocking APIs—it becomes

clear.

Programming is chock-full of backwardisms like these, and Node.js is no

exception. Starting out, you’ll frequently run into code that looks like it should

work one way, but it actually does something quite different.

That’s OK! With this book, you’ll learn Node by making compact programs

that interact in useful ways. As we run into more of Node’s backwardisms,

we’ll dive in and explore them.

Aspects of Node.js Development

Node.js is a surprisingly big subject, so let’s break it down into different

aspects. There are many aspects of Node.js development we might talk about,

ranging from basic JavaScript syntax to revision control. This book focuses

on five in particular:

• Practical programming

• Architecture and core

• Patterns

• JavaScriptisms

• Supporting code

Let’s explore each of these briefly.

Practical Programming

Practical programming is all about producing real code that does something

useful. Interacting with a file system, establishing socket connections, or

serving web applications are all examples of practical programming.

Each of the remaining chapters of this book focuses on one particular practical

domain. Through code examples specific to each domain, you’ll learn Node’s

architecture, patterns, JavaScriptisms, and supporting code.

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Architecture and Core

Understanding Node’s architecture will help you to harness its features while

avoiding performance-crushing pitfalls. For example, Node uses an event loop

written in C for scheduling work. But it executes application code in a Java-

Script environment. How information is shuttled between these layers is the

kind of impactful architectural detail you’ll learn.

Patterns

Like any successful codebase with a healthy ecosystem, Node.js has a number

of repeating patterns. Some of these patterns are baked into the core while

others mostly appear in third-party libraries. Examples include the use of

callbacks, error-handling techniques, and classes like

EventEmitter

and

Stream

which are used liberally for event dispatching.

As we progress through different practical programming domains, we’ll natu-

rally encounter these and other patterns. When we do, you’ll discover why

they’re useful and how to use them effectively.

JavaScriptisms

JavaScript is the language of Node programs, so you’ll be seeing quite a lot

of it. The code examples in this book make use of the latest available Java-

Script features. Some of these features may be unfamiliar to you, even if

you’ve done JavaScript development before.

JavaScriptisms discussed in this book include things like the nature of

functions and object inheritance. ECMAScript Harmony—the code name for

the next version of the JavaScript spec—packs some new features we’ll use,

too.

Supporting Code

Code does not live in isolation; it takes a village to support any individual

program. Supporting code covers lots of things, from unit testing to perfor-

mance benchmarks to deployment scripts. We’ll use supporting code

throughout the book to make our programs more robust, more scalable, and

more manageable.

With these five aspects, you’ll be able to develop applications that make the

most use out of the platform while using idiomatic Node.js style. The example

applications you’ll develop in this book are functional and small, and aim to

clearly demonstrate the five aspects. But to use them, you’ll need to get Node.js

installed first.

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精通Node.js：正确之道

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