Node.js实战：超越Web开发

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"Node.js the Right Way" 《Node.js the Right Way》是一本专注于Node.js的入门级技术书籍，旨在帮助读者快速掌握现代服务器端JavaScript编程。作者深入浅出地介绍了Node.js的基础机制，并且超越了基本的Web开发范畴，探讨了如何构建高质量的服务器端应用。本书得到了业界专家的高度评价，他们认为它不仅适合初学者，也适合想要拓宽视野的JavaScript开发者。Allen Wirfs-Brock，作为ECMAScript语言规范的项目编辑，称赞本书能够引领读者深入了解构建优质服务器端应用所需的知识。Rick Waldron，软件工程师，认为对于刚开始接触Node.js的人来说，这本书是唯一需要的资料，足以替代其他学习材料。Eric Redmond，七库数据库的合著者，指出本书揭示了Node.js远不止是一种为潮人设计的轻量级、大规模应用服务器，而是拥有更广泛的应用潜力。Xavi Ramirez，Baydin公司的开发者，表示这本书通过实用的例子快速展示了Node.js的灵活性和强大功能，非常适合想要探索服务器基础设施的JavaScript开发者。书中跳过了通常的“Hello World”入门示例，直接进入实用的应用示例，让读者能够快速理解并应用Node.js。内容可能包括但不限于以下几个关键知识点： 1. **事件驱动编程**：Node.js的核心特性之一就是其基于事件循环的非阻塞I/O模型，这使得Node.js能处理大量并发连接，适用于实时应用。 2. **模块系统**：Node.js的模块系统允许开发者通过`require`命令来导入和使用其他代码模块，这有助于代码组织和重用。 3. **V8引擎**：Node.js使用Google的V8 JavaScript引擎，使得JavaScript在服务器端运行速度得到大幅提升，同时也支持服务器端执行高性能的JavaScript代码。 4. **网络编程**：讲解如何使用Node.js进行HTTP、HTTPS、TCP或UDP等网络通信，创建Web服务器和客户端。 5. **文件系统操作**：介绍如何读取、写入、创建和管理文件系统，这是许多服务器端任务的基础。 6. **包管理器npm**：Node.js的包管理器npm是最大的开源软件包库之一，学习如何使用npm安装、发布和管理依赖。 7. **异步编程**：包括回调函数、Promise和async/await等异步编程模式，以解决回调地狱问题，提高代码可读性和可维护性。 8. **性能优化**：探讨如何通过工具和最佳实践来优化Node.js应用程序，如内存管理和性能监控。 9. **测试和调试**：介绍如何对Node.js应用进行单元测试、集成测试以及调试技巧，确保代码质量和稳定性。 10. **安全考虑**：讨论Node.js应用的安全问题，如数据验证、错误处理和防止注入攻击等。通过这些内容的学习，读者不仅能了解Node.js的基本用法，还能深入理解如何利用Node.js构建健壮、高效且易于维护的服务器端应用程序。无论是Web开发者寻求扩展技能，还是对服务器端编程感兴趣的技术人员，这本书都能提供宝贵的指导。

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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