JavaScript has a high level of expressiveness. This makes it possible to mix functional and object-oriented programming. Modern JavaScript is not solely OOP or functional—it is a mixture of the two. Concepts such as Strategy Pattern and mixins are perfect for JavaScript's prototype structure, and they help to prove that today's best practices in JavaScript share equal amounts of functional programming and object-oriented programming.

If you were to take away only one thing from this book, I would want it to be how to apply functional programming techniques to real-world applications. And this chapter showed you how to do exactly that.