JavaScript is not a functional programming language. That is not to say that it isn't possible to apply some of the ideas from functional programming to it. These approaches enable cleaner, easier to debug code. Some might even argue that the number of issues will be reduced although I have never seen any convincing studies on that.

In this chapter we looked at six different patterns. Lazy instantiation, memoization, and immutability are all creational patterns. Function passing is a structural pattern as well as a behavioral one. Accumulators are also behavioral in nature. Filters and pipes don't really fall into any of the GoF categories so one might think of them as a style pattern.

In the next chapter we'll look at a number of patterns for dividing the logic and presentation in applications. These patterns have become more important as JavaScript applications have grown.