（翻译）《Hands-on Node.js》—— 引言

Introduction

At the European JSConf 2009, a young programmer by the name of Ryan Dahl, introduced a project
he had been working on. This project was a platform that combined Google’s V8 JavaScript engine
and an event loop to create a server-side platform programmable in JavaScript. The project took a
different direction from other server-side JavaScript platforms: all I/O primitives were event-driven,
and there was no way around it. Leveraging the power and simplicity of JavaScript, it turned the
difficult task of writing asynchronous applications into an easy one. Since receiving a standing
ovation at the end of his talk, Dahl’s project has been met with unprecedented growth, popularity
and adoption.
The project was named Node.js, now known to developers simply as ‘Node’. Node provides purely
evented, non-blocking infrastructure for building highly concurrent software.
Node allows you to easily construct fast and scalable network services.

Why the sudden, exponential popularity?

Server-side JavaScript has been around for some time, what makes this platform so appealing?
In previous server-side JavaScript implementations, javascript was the raison d’etre, and the
approach focussed on translating common practices from other platforms like Ruby, PERL and
Python, into JavaScript. Node took a leap from this and said: “Let’s use the successful event-driven
programming model of the web and use it to make an easy way to build scalable servers. And let’s
make it the only way people can do anything on this platform.”.
It can be argued that JavaScript itself contributed to much of Node’s success, but that would not
explain why other the server-side projects proceeding Node have not yet come close in popularity.
The ubiquity of JavaScript surely has played a role, but, as Ryan Dahl points out, unlike other Serverside
JavaScript attempts, unifying the client and server into a common language was not the primary
goal for Node.
In my perspective there are three factors contributing to Node’s success:
1. Node is Easy - Node makes event-driven I/O programming, the best way to do I/O programming,
much easier to understand and achieve than in any other existing platform.
2. Node is Lean - Node does not try to solve all problems. It lays the foundation and supports
the basic internet protocols using clean, functional APIs.
3. Node does not Compromise - Node does not try to be compatible with pre-existing software,
it takes a fresh look at what many believe is the right direction.

What does this book cover?

We will analyze what makes Node a different proposal to other server-side solutions, why you
should use it, and how to get started. We will start with an overview but quickly dive into some
code module-by-module. By the end of this book you should be able to build and test your own
Node modules, service producers/consumers and feel comfortable using Node’s conventions and
API.

What does this book not cover?

This book does not attempt to cover the complete Node API. Instead, we will cover what the author
thinks is required to build most applications he would build on Node.
This book does not cover any Node frameworks; Node is a great tool for building frameworks and
many are available, such as cluster management, inter-process communication, web frameworks,
network traffic collection tools, game engines and many others. Before you dive into any of those
you should be familiar with Node’s infrastructure and what it provides to these building blocks.

Prerequisites

This book does not assume you have any prior knowledge of Node, but the code examples are written
in JavaScript, so familiarity with the JavaScript language will help.

Exercises

This book has exercises in some chapters. At the end of this book you can find the exercise
solutions, but I advise you to try do them yourself. Consult this book or use the comprehensive
API documentation on the official http://nodejs.org¹ website.

Source code

You can find some of the source code and exercises used in this book on GitHub:
https://github.com/pgte/handson_nodejs_source_code²
or you can download it directly:
https://github.com/pgte/handson_nodejs_source_code/zipball/master³

Where will this book lead you?

By the end of it, you should understand the Node API and be able to pursue the exploration of other
things built on top of it, being adaptors, frameworks and modules.
Let’s get started!