Node.js实战：基础与应用开发

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“Node.js in Action”是一本关于Node.js技术的专著，通过Manning Early Access Program（MEAP）在2012年发行了第10版。这本书旨在深入探讨Node.js的基础以及如何利用它进行web应用开发，并进一步拓展到更高级的主题。本书共分为三个部分：第一部分“Node基础”： 1. 第1章“为什么网络需要Node.js”：讨论了Node.js在处理高并发、实时Web应用中的优势，以及其非阻塞I/O模型对提升性能的影响。 2. 第2章“开始使用Node.js”：介绍了Node.js的安装、基本架构以及如何编写第一个Node.js程序，帮助初学者快速入门。 3. 第3章“异步编程”：详细讲解了Node.js的核心特性——异步事件驱动编程，包括回调函数、事件循环和Promise等概念。第二部分“使用Node.js开发Web应用”： 4. 第4章“构建Node.js Web应用”：涵盖了创建HTTP服务器、路由处理和响应管理等Web开发基础。 5. 第5章“存储Node.js应用数据”：讨论了与数据库的集成，如MongoDB等，以及如何进行数据操作。 6. 第6章“测试Node.js应用”：介绍单元测试、集成测试和持续集成工具，确保代码质量和稳定性。 7. 第7章“Connect”：讲解了Connect框架，它是构建中间件栈的强大工具。 8. 第8章“Connect的内置中间件”：详细阐述了Connect框架内各种中间件的使用和功能。 9. 第9章“Express”：Express是基于Connect的流行Web应用框架，本章讲解如何利用它构建复杂的应用。 10. 第10章“Web应用模板”：介绍了模板引擎，如Jade或EJS，用于动态生成HTML页面。 11. 第11章“部署Node.js Web应用”：涵盖了应用部署策略、负载均衡和生产环境优化等内容。第三部分“更深入的Node.js探索”： 12. 第12章“超越Web服务器”：探讨了Node.js在其他领域的应用，如命令行工具、桌面应用等。 13. 第13章“Node.js生态系统”：介绍了Node.js的模块系统、npm包管理和社区资源，展示了丰富的第三方库和工具。此外，书本还附有三个附录： 14. 附录A“在Windows上使用Cygwin安装Node.js”：提供了在Windows环境下安装Node.js的详细指南。 15. 附录B“调试Node.js应用”：讲述了调试工具和技巧，帮助开发者找出和修复问题。 16. 附录C“创建文档”：介绍了如何为Node.js项目编写清晰易懂的文档，提高项目的可维护性。这本书全面地覆盖了Node.js的基础到高级应用，对于想要学习和深入理解Node.js的开发者来说，是一份宝贵的学习资料。

NOTE

Monkey patching

Monkey patching is a powerful programming technique for dynamic

languages that you can take advantage of when developing in

Node. In non-dynamic, static languages, once a function or class

has been defined, it can't be altered during program execution. In

dynamic languages, you can simply redefine a function or class. If

you've previously developed using languages that don't easily allow

this, like PHP or Java, the capability may seem unusual, but in

practice you'll likely grow to love the flexibility it provides.

JavaScript is also a perfect companion to Node because it has the advantage of

being portable between the browser and the server. As long as any APIs accessed

by logic are available on both browser and server, the same logic should run in

either environment. Form validation, for example, is often duplicated in the client

and server. Why write the same code twice? Reusing logic in both the browser and

server enforces consistancy and means not having to reinvent the wheel. It also

means you have to maintain less code. Another benefit you'll find when working in

Node is you don't have to mentally context switch between languages when

working on different parts of a web application. Staying in one language is likely

to increase your productivity and make development more enjoyable.

1.2.4 Advancing the idea of the application server

In addition to the concept of asynchronous development and server-side

avaScript, another idea that may be new to you if you come from a PHP

background is the idea of writing a web application server instead of page scripts.

Unlike PHP, developing in some web development frameworks, such as Ruby on

Rails or the Python-based Django web framework, involves writing a server that

sends and receives HTTP. Web development using Node follows the same

principle.

Application servers give you more control than writing PHP scripts that get

riggered by a web server such as Apache. Writing a web application with clean

URL support in PHP requires you to use web server rewrite functionality (such as

Apache's mod_rewrite). Rewrite functionality generally translates the path portion

of the URL into a global variable PHP can access. Most web application servers

require no such hacks.

As opposed to writing a PHP script, when writing a Node web application

erver we interface primarily with a request and a response object. The request

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object contains details about the web client making the request and what they are

requesting. The response object contains methods that allow you to send data to the

web client. Many frameworks exist that leverage the request and response objects

to provide functionality commonly needed in web applications. The most popular,

called Express, we cover in chapter 8.

Node add-on frameworks generally include functionality to associate URL

patterns with related logic, provide session support, help render data to HTML, and

allow media files, such as images, to be served as content. These frameworks

generally follow the time-tested Model-view-controller (MVC) design pattern.

NOTE

MVC

The MVC design pattern is a way of organizing applications that

eparates data, data manipulation logic, and output. In the context

of web applications, the "model" is usually manipulated using a

database API or an object that provides a higher level interface to

data. The "view" portion of the architecture is usually represented

by templates. The "controller" is the logic that manages the flow of

data from the model to the view (and input from the view back to

the model). If you don't have experience with MVC, Jeff Atwood's

online article "Understanding Model-View-Controller"

provides a

good introduction to the concept. If you don't get it immediately,

don't worry: you'll likely gain an understanding of the concept as

you read through this book.

Footnote 3m

http://www.codinghorror.com/blog/2008/05/understanding-model-view-controller.html

Now that you've seen how Node is different from established frameworks, in its

design choices and use of asynchrous programming and JavaScript, let's look

further at one more reason why the web of today and tomorrow needs Node:

Node's ability to do more.

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1.3 Node can do more

Node's capabilties go beyond that of traditional web frameworks. A Node web

application, for example, can easily integrate support for non-HTTP protocols,

such as WebSocket. Node is flexible and powerful enough that it can be used to

implement TCP/IP applications such as a reverse HTTP proxy, caching web

requests from a slower, non-Node web server (emulating the functionality of

special-purpose applications like Squid and Varnish). Node can even be used to

develop entirely new TCP/IP protocols.

In this section we'll look at a few ways Node is being used to develop non-web

pplications. While you may be predominantly interested in Node's use for web

application development, knowing the full spectrum of Node's capabilties may lead

you to use Node in unexpected ways.

1.3.1 Server applications

Node has been used to implement versions of a variety of traditional server

pplications. Node-based DNS servers, web crawlers, message queue servers, and

many other types of applications exist.

Server applications - such as file transfer, email delivery, and instant messaging

pplications - have traditionally been created in non-dynamic languages such as C,

C++, and Java. C is a very flexible and powerful language, but is comparatively

low-level and can be challenging to learn. C++ significantly extends C, but offers a

cornucopia of language features that, if not used correctly, allows you to "shoot

yourself in the foot" (the ability to redefine operators like "+" is one example). Java

has fewer sharp edges than C++, but is more verbose than C and less flexible than

dynamic languages.

As we mentioned earlier, Node breaks from tradition and leverages JavaScript

hich makes it accessible to a large number of programmers. Given JavaScript's

strengths, if Node is widely adopted by server developers the result will likely be

quicker application development and increased diversity in server software.

Browserling, shown in figure 1.6, is an example of a Node-based website that

akes great use of Node's non-web capabilities behind the scenes. The site allows

in-browser use of other browsers, including the notorious Internet Explorer 6. This

is extremely useful to front-end web developers as it frees them from having to

install numerous browsers and operating systems solely for testing. Browserling

leverages a Node-driven project called StackVM which manages virtual machines

(VMs), created using the QEMU ("Quick Emulator") emulator. QEMU emulates

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support it. The popular Socket.io project, which implements a robust Node-driven

WebSocket server, is a good example of Node being used with emerging protocols.

If you're a die-hard dreaming about trying out protocol development, Node may

be just the technology you've been waiting for.

1.3.3 Command-line applications

The things that make Node perfect for server and protocol development also make

ode a great candidate for the development of command-line interface (CLI)

applications. Examples of common CLI applications include version control

applications, database clients, and compilers. In addition to its networking API,

Node offers access to functionality commonly needed by CLI applications:

filesystem, process, and operating system functionality.

The Node community has created modules that make CLI appliction

evelopment easy by elegantly handling option and command parsing. The

combination of the familiar JavaScript language with Node's elegant APIs and easy

CLI parsing has the potential to unleash the creativity of many who have, until

now, only dabbled in CLI application creation.

1.3.4 Screen scraping

A less traditional type of application that Node is perfect for is the "screen

craper". Screen scraping is the art of parsing web pages to extract data. Node is,

more than another other web framework, suited for this task because Node is

capable of emulating web browser functionality.

Because Node is built using Google's V8 JavaScript engine, Node speaks the

ame logical language as the browser. JSDOM, a Node community add-on,

leverages this capability, allowing Node to emulate the web browser's Document

Object Model (DOM).

The DOM is essential for web browser emulation, acting as a

avaScript-accessible interface to HTML/CSS content. By emulating the DOM,

Node can read and write HTML in a virtual browser. Node can then take advantage

of high level JavaScript libraries, like JQuery, that allow high-level manipulation

and querying of the DOM.

Following is an example of using JQuery and a community-created Node

module to traverse the DOM in a virtual browser:

var jsdom = require("jsdom");

jsdom.env("http://releases.ubuntu.com", [

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