Book Image

Node.js Design Patterns

By : Mario Casciaro
Book Image

Node.js Design Patterns

By: Mario Casciaro

Overview of this book

Node.js is a massively popular software platform that lets you use JavaScript to easily create scalable server-side applications. It allows you to create efficient code, enabling a more sustainable way of writing software made of only one language across the full stack, along with extreme levels of reusability, pragmatism, simplicity, and collaboration. Node.js is revolutionizing the web and the way people and companies create their software. In this book, we will take you on a journey across various ideas and components, and the challenges you would commonly encounter while designing and developing software using the Node.js platform. You will also discover the "Node.js way" of dealing with design and coding decisions. The book kicks off by exploring the fundamental principles and components that define the platform. It then shows you how to master asynchronous programming and how to design elegant and reusable components using well-known patterns and techniques. The book rounds off by teaching you the various approaches to scale, distribute, and integrate your Node.js application.
Table of Contents (16 chapters)
Node.js Design Patterns
Credits
About the Author
Acknowledgments
About the Reviewers
www.PacktPub.com
Preface
Index

Asynchronous control flow with streams


Going through the examples that we presented so far, it should be clear that streams can be useful not only to handle I/O, but also as an elegant programming pattern that can be used to process any kind of data. But the advantages do not end at the simple appearance; streams can also be leveraged to turn asynchronous control flow into flow control, as we will see in this section.

Sequential execution

By default, streams will handle data in a sequence, for example, a _transform() function of a Transform stream will never be invoked again with the next chunk of data, until the previous invocation completes by executing callback(). This is an important property of streams, crucial for processing each chunk in the right order, but it can also be exploited to turn streams into an elegant alternative to the traditional control flow patterns.

Some code is always better than too much explanation, so let's work on an example to demonstrate how we can use streams...