Node.js is considered by many as a game-changer—the biggest shift of the decade in web development. It is loved not just for its technical capabilities, but also for the paradigm shift that it introduced in web development.
First, Node.js applications are written in JavaScript, the language of the web, the only programming language supported natively by a majority of web browsers. This aspect enables scenarios such as single-language application stacks and sharing of code between the server and the client. Node.js itself is contributing to the rise and evolution of the JavaScript language. People realize that using JavaScript on the server is not as bad as it is in the browser, and they will soon start to love it for its pragmatism and for its hybrid nature, halfway between object-oriented and functional programming.
The second revolutionizing factor is its single-threaded, asynchronous architecture. Besides obvious advantages from a performance and scalability point of view, this characteristic changed the way developers approach concurrency and parallelism. Mutexes are replaced by queues, threads by callbacks and events, and synchronization by causality.
The last and most important aspect of Node.js lies in its ecosystem: the npm package manager, its constantly growing database of modules, its enthusiastic and helpful community, and most importantly, its very own culture based on simplicity, pragmatism, and extreme modularity.
However, because of these peculiarities, Node.js development gives you a very different feel compared to the other server-side platforms, and any developer new to this paradigm will often feel unsure about how to tackle even the most common design and coding problem effectively. Common questions include: "How do I organize my code?", "What's the best way to design this?", "How can I make my application more modular?", "How do I handle a set of asynchronous calls effectively?", "How can I make sure that my application will not collapse while it grows?", or more simply "What's the right way of doing this?" Fortunately, Node.js has become a mature enough platform and most of these questions can now be easily answered with a design pattern, a proven coding technique, or a recommended practice. The aim of this book is to guide you through this emerging world of patterns, techniques, and practices, showing you what the proven solutions to the common problems are and teaching you how to use them as the starting point to building the solution to your particular problem.
By reading this book, you will learn the following:
The "Node way":
How to use the right point of view when approaching a Node.js design problem. You will learn, for example, how different traditional design patterns look in Node.js, or how to design modules that do only one thing.
A set of patterns to solve common Node.js design and coding problems:
You will be presented with a "Swiss army knife" of patterns, ready-to-use in order to efficiently solve your everyday development and design problems.
How to write modular and efficient Node.js applications:
You will gain an understanding of the basic building blocks and principles of writing large and well-organized Node.js applications and you will be able to apply these principles to novel problems that don't fall within the scope of existing patterns.
Throughout the book, you will be presented with several real-life libraries and technologies, such as LevelDb, Redis, RabbitMQ, ZMQ, Express, and many others. They will be used to demonstrate a pattern or technique, and besides making the example more useful, these will also give you great exposure to the Node.js ecosystem and its set of solutions.
Whether you use or plan to use Node.js for your work, your side project, or for an open source project, recognizing and using well-known patterns and techniques will allow you to use a common language when sharing your code and design, and on top of that, it will help you get a better understanding of the future of Node.js and how to make your own contributions a part of it.
Chapter 1, Welcome to the Node.js Platform, serves as an introduction to the world of Node.js application design by showing the patterns at the core of the platform itself. It covers the Node.js ecosystem and its philosophy, a short introduction to Node.js version 6, ES2015, and the reactor pattern.
Chapter 2, Node.js Essential Patterns, introduces the first steps towards asynchronous coding and design patterns with Node.js discussing and comparing callbacks and the event emitter (observer pattern). This chapter also introduces the Node.js module system and the related module pattern.
Chapter 3, Asynchronous Control Flow Patterns with Callbacks, introduces a set of patterns and techniques for efficiently handling asynchronous control flow in Node.js. This chapter teaches you how to mitigate the "callback hell" problem using plain JavaScript and the async library.
Chapter 4, Asynchronous Control Flow Patterns with ES2015 and Beyond, progresses with the exploration of asynchronous control flows introducing Promises, Generators, and Async-Await.
Chapter 5, Coding with Streams, dives deep into one of the most important patterns in Node.js: streams. It shows you how to process data with transform streams and how to combine them into different layouts.
Chapter 6, Design Patterns, deals with a controversial topic: traditional design patterns in Node.js. It covers the most popular conventional design patterns and shows you how unconventional they might look in Node.js. It also introduces the reader to some emerging design patterns that are specific only to JavaScript and Node.js.
Chapter 7, Wiring Modules, analyzes the different solutions for linking the modules of an application together. In this chapter, you will learn design patterns such as Dependency Injection and service locator.
Chapter 8, Universal JavaScript for Web Applications, explores one of the most interesting capabilities of modern JavaScript web applications: being able to share application code between the frontend and the backend. Across this chapter we learn the basic principles of Universal JavaScript by building a simple web application with React, Webpack, and Babel.
Chapter 9, Advanced Asynchronous Recipes, takes a problem-solution approach to show you how some common coding and design challenges can be solved with ready-to-use solutions.
Chapter 10, Scalability and Architectural Patterns, teaches you the basic techniques and patterns for scaling a Node.js application.
Chapter 11, Messaging and Integration Patterns, presents the most important messaging patterns, teaching you how to build and integrate complex distributed systems using ZMQ and AMQP.
To experiment with the code, you will need a working installation of Node.js version 6 (or greater) and npm 3 (or greater). Some examples will require you to use a transpiler such as Babel. You will also need to be familiar with the command prompt, know how to install an npm package, and know how to run Node.js applications. You will also need a text editor to work with the code and a modern web browser.
This book is for developers who have already had initial contact with Node.js and now want to get the most out of it in terms of productivity, design quality, and scalability. You are only required to have some prior exposure to the technology through some basic examples, since this book will cover some basic concepts as well. Developers with intermediate experience in Node.js will also find the techniques presented in this book beneficial.
Some background in software design theory is also an advantage to understand some of the concepts presented.
This book assumes that you have a working knowledge of web application development, JavaScript, web services, databases, and data structures.
In this book, you will find a number of text styles that distinguish between different kinds of information. Here are some examples of these styles and an explanation of their meaning.
Code words in text, database table names, folder names, filenames, file extensions, pathnames, dummy URLs, user input, and Twitter handles are shown as follows: "ES2015 introduces the let keyword to declare variables that respect the block scope."
A block of code is set as follows:
const zmq = require('zmq')
const sink = zmq.socket('pull');
sink.bindSync("tcp://*:5001");
sink.on('message', buffer => {
console.log(`Message from worker: ${buffer.toString()}`);
});When we wish to draw your attention to a particular part of a code block, the relevant lines or items are set in bold:
function produce() {
//...
variationsStream(alphabet, maxLength)
.on('data', combination => {
//...
const msg = {searchHash: searchHash, variations: batch};
channel.sendToQueue('jobs_queue',
new Buffer(JSON.stringify(msg)));
//...
})
//...
}Any command-line input or output is written as follows:
node replier node requestor
New terms and important words are shown in bold. Words that you see on the screen, for example, in menus or dialog boxes, appear in the text like this: "To explain the problem, we will create a little web spider, a command-line application that takes in a web URL as the input and downloads its contents locally into a file."
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