Mastering JavaScript Promises (2015)

Preface

In this book, we will explore the concept and implementation of promises in JavaScript. This book has an evolving context that will lead you from a beginner's level to the master level of promises. Every chapter of this book will give you an outline to achieve a specific goal that will help you realize and quantify the amount of knowledge you absorb in every chapter.

The entire stack of chapters is designed in a way such that the book will evolve as you go through it. Every chapter in this book is designed in two parts: one is the concept building part and the other is the experimenting part, where you will be able to sample snippets of concepts, sometime in code, sometimes in best practices, and sometimes in images.

The first four chapters are more or less like theoretical knowledge to provide you with a solid foundation on JavaScript and promises. So, if you're a novice and don't know anything about JavaScript or promises, you will learn a great deal with these chapters. The rest of the chapters are more technology-oriented and you will learn implementation of promises in WinRT, Angular.js, jQuery, and Node.js. So, if you are a professional and already have some idea of promises, you may jump right into Chapter 5, Promises in WinRT, but I'd prefer it if you read through all the chapters for a better understanding of this book.

We will start with the introduction to JavaScript and how it has seen ups and downs from the late 90s up to the first decade of the twenty first century. We will focus on what asynchronous programing is and how JavaScript is using it. Moving on, I will introduce promises and its impact and how it's implemented. To make the book interesting and impart more knowledge to you, I will show you how promises has made its place in the heart of Java, one of the most mature object-oriented programming languages. This add-on content will act as a detour and clarify concepts in a more efficient way.

The flow of book will then lead you to the implementation of promises in some of the most used JavaScript libraries. We will see a sample code on how the mechanism of these libraries work. Finally, we will wrap up the book with our last chapter that will show you what is coming next in JavaScript, why it has gained so much attention over the past few years and what would be the possible future of JavaScript.

What this book covers

Chapter 1, Promises.js, covers the history of JavaScript and how it shaped into one of the leading technologies in modern application development. We will discuss why there was a need of JavaScript in the early 90s and how this language has seen ups and downs throughout its existence.

Chapter 2, The JavaScript Asynchronous Model, explains what a programming model is and how they are implemented in different languages, starting from a simple programming model to the synchronous model to the asynchronous model. We will also see how tasks are organized in memory and how they will serve according to their turns and priorities and how programming models decide what task is to be served.

Chapter 3, The Promise Paradigm, covers the paradigm of promise and the concept behind it. We will learn the conceptual knowledge of promise, deferred, common sequence of promise, and how promise helps in decoupling the business logic and application logic. We will also learn about the relationship between promises and event emitters and the concept behind the relation between promises and event emitters.

Chapter 4, Implementing Promises, discusses why we are implementing promises and why we chose Java as the core subject of this chapter. Java has richer features than any other programming language, and it also has better mechanism for asynchronous behavior. This chapter is the point where we start our journey to master promises.

Chapter 5, Promises in WinRT, explains how promises can be implemented in WinRT. We will see how promises evolved on the Windows platform and how it's contributing to different Windows-based devices.

Chapter 6, Promises in Node.js, covers what Node.js is, from where this most amazing library has evolved, who built it, and why and how it's helping us to create real-time web apps. We will see Q, the best way to offer promises to Node.js. We will see how we can work with Q, and then we will see different ways of using Q along with Node.js.

Chapter 7, Promises in Angular.js, explains how promises will be implemented in Angular.js, how it evolved and how promises will help in achieving applications composed for real-time web apps. We will also see the functionality of the Q library and the Angular.js implementation of promises using code and learn how to use them in our next application.

Chapter 8, Promises in jQuery, discusses how jQuery started taking shape and how it became a fundamental element of the modern-day web development. We will learn how to build basic jQuery documents and how to call the functions embedded into HTML files. We will learn why we started using deferred and promise in jQuery and how they are helping us to create cutting edge applications on both web-based platform and portable devices.

Chapter 9, JavaScript – The Future Is Now, covers how JavaScript is a game changer and how it has a bright future ahead. We will also explore why JavaScript has great tendency and adoptability, which will lead it to the next level of usage in almost every domain of computer science.

What you need for this book

If you are a software engineer who wants to learn more interesting facts about JavaScript to make your life easier, this book is for you. A simple and engaging language with narrations and code examples makes this book easy to understand and apply its practices. This book starts with an introduction to JavaScript promises and how it evolved over time. You will then learn the JavaScript asynchronous model and how JavaScript handles asynchronous programming. Next, you will learn about the promises paradigm and its advantages. Finally, this book will show you how to implement promises on platforms such as WinRT, jQuery, and Node.js, which are used in project development.

To get the best out of this book, you should know the basic programming concepts, the basic syntax of JavaScript, and possess a good understanding of HTML.

Who this book is for

This book is for all the software/web engineers who want to apply the promises paradigm in their next project and get the best outcome from it. This book has all the basic as well as advanced concepts of promises in JavaScript. This book can also act as a reference for the engineers who are already using promises in their projects and want to improve their current knowledge of this concept.

This book is a great resource for frontend engineers, but also serves as a learning guide for backend engineers who want to make sure their code collaborates seamlessly within the project.

Conventions

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: "The click function will call (or execute) the callback function we passed to it."

A block of code is set as follows:

Q.fcall(imException)

.then(

// first handler-fulfill

function() { },

);

Any command-line input or output is written as follows:

D:\> node –v

D:\> NPM –v

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: " It should turn into green and display the Success message."

Note

Warnings or important notes appear in a box like this.

Tip

Tips and tricks appear like this.