Preface

Over the last few years, JavaScript has emerged as one the most popular programming languages, expanding its reach from its original browser environment to server runtimes, databases, and to mobile, embedded, or desktop applications. The sixth edition of its specification ECMAScript 2015 (ES6) was a major milestone that brought JavaScript features in line with other popular programming languages. The community and the browser vendors stepped up their efforts to support ES6, and we should see full support for the standard across multiple JavaScript engines as soon as early 2016. The future of JavaScript beyond ES6 looks very promising as its standardization effort aims to release a new specification every year.

In summer 2015, JavaScript was the most popular language used on the GitHub repository hosting service and had the biggest number of packages compared to all other languages. This change in popularity was made possible by an intense process of creation and refinement of libraries and frameworks alongside an improvement in development standards and practices throughout the JavaScript community. One of these modern JavaScript libraries is jQuery, the most popular browser library, which was a great facilitator in speeding up the adoption of common web standards across browser engines. Similarly, at least in impact, the Underscore library brought uniformity and functional programming features to JavaScript while bridging the gap between client and server environments.

Underscore represents a model of code quality and community involvement that other libraries should try to emulate, and many libraries were inspired or built upon Underscore. Throughout this book, Underscore proved to be the perfect vehicle to explore programming concepts that apply to any type of application. It is also a great example for the concept of universal JavaScript where the same code can be executed in multiple environments. For a JavaScript developer, Underscore is the JavaScript-based library that can be used to create code that runs everywhere or as a foundation for adopting a functional programming style.

JavaScript has become an important language in enterprise software development with the adoption of the Node.js runtime by companies such as Microsoft, IBM, and Intel to name just a few. The considerable rise in popularity of single page application frameworks, such as Backbone.js, AngularJS, React, and many others, means that developers are writing more complex JavaScript code with an increased effort in managing the increase in complexity. Adopting standards such as ES6 and using Underscore or similar libraries should help in coping with the challenges of the rapidly and continuously changing industry.