Do we need to know advanced math—category theory, Lambda calculus, polymorphisms—just to write applications with functional programming? Do we need to reinvent the wheel? The short answer to both these questions is no.

In this chapter, we will do our best to survey everything that can impact the way we write our functional applications in JavaScript.

Please understand that the current landscape of functional libraries for JavaScript is a very fluid one. Like all aspects of computer programming, the community can change in a heartbeat; new libraries can be adopted and old ones can be abandoned. For instance, during the writing process of this very book, the popular and stable Node.js platform for I/O has been forked by its open source community. Its future is vague.

Therefore, the most important concept to be gained from this chapter is not how to use the current libraries for functional programming, but how to use any library that enhances JavaScript's functional programming method. This chapter will not focus on just one or two libraries, but will explore as many as possible with the goal of surveying all the many styles of functional programming that exist within JavaScript.