Explore the Underscore.js library by example using a test-driven development approachAbout This BookUnderstand and learn to apply functional programming principles using the built-in functions of Underscore.js Leverage and reuse Underscore.js-based code to create code that targets client, server, or database contexts Take Underscore.js further by reusing code between client and server and by learning about other closely related librariesWho This Book Is ForIf you are a developer with fundamental JavaScript knowledge and want to use modern JavaScript libraries to extend your functional programming skills, then Underscore.js is an important library you should be familiar with.What You Will LearnReference and call Underscore.js functions using a modern JavaScript development workflow Apply Underscore.js to JavaScript arrays, objects, and functions Take advantage of object-oriented or functional programming techniques with Underscore.js Leverage Underscore.js to create code that targets client, server, or database contexts Extend Underscore.js functionality with other closely related libraries Reuse Underscore.js-based code between client and server applications Prepare for the upcoming JavaScript standard ECMAScript 6 and support older browsersIn DetailUnderscore.js is one of the most popular modern JavaScript libraries used for functional programming. It can be used as a base for building complex JavaScript applications in a sustainable manner and for building other JavaScript libraries. It embraces functional programming principles but is not opinionated and can be used with imperative, object-oriented, functional, or other programming styles.This book explores how to use Underscore.js to power your code and understand modern JavaScript development concepts while applying a lightweight and efficient workflow to build applications.The book starts with an incremental Underscore.js introduction by exploring key JavaScript concepts. You will then explore the basic features of Underscore.js in action and establish a lightweight development workflow that allows the provided examples to be guided by tests. The book then covers the functionality of Underscore.js with in-depth examples and explanations for understanding and applying the Underscore.js API. You'll also learn how to use Underscore.js as a base for your own modules and libraries within an object-oriented or functional programming style, and will be able to explore Underscore.js use cases in different environments.Eventually, you'll learn about libraries that are closely related with Underscore.js, how to share code between client and server, and how to prepare for the upcoming JavaScript standard ECMAScript 6.Style and approachThis book takes an example-driven approach to describing some of the essential JavaScript concepts and practices that are useful for building sustainable applications.