Book Image

Node.js Design Patterns - Second Edition

By : Luciano Mammino, Purra, Mario Casciaro
Book Image

Node.js Design Patterns - Second Edition

By: Luciano Mammino, Purra, 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 basics of Node.js describing it's asynchronous single-threaded architecture and the main design patterns. It then shows you how to master the asynchronous control flow patterns,and the stream component and it culminates into a detailed list of Node.js implementations of the most common design patterns as well as some specific design patterns that are exclusive to the Node.js world.Lastly, it dives into more advanced concepts such as Universal Javascript, and scalability' and it's meant to conclude the journey by giving the reader all the necessary concepts to be able to build an enterprise grade application using Node.js.
Table of Contents (12 chapters)

Promise

We mentioned in the previous chapters that Continuation Passing Style (CPS) is not the only way to write asynchronous code. In fact, the JavaScript ecosystem provides interesting alternatives to the traditional callback pattern. One of the most famous alternatives is promise, which is getting more and more attention, especially now that it is part of ECMAScript 2015 and has been natively available in Node.js since version 4.

What is a promise?

In very simple terms, promise is an abstraction that allows a function to return an object called promise, which represents the eventual result of an asynchronous operation. In the promises jargon, we say that a promise is pending when the asynchronous operation is not yet complete, it's fulfilled when the operation successfully completes, and rejected when the operation terminates with an error. Once a promise is either fulfilled or rejected, it's considered settled.

To receive the fulfillment value or the error (reason) associated...