In this chapter, we learned how to implement a Set class from scratch, which is similar to the Set class defined in the definition of ECMAScript 6. We also covered some methods that are not usually in other programming language implementations of the set data structure, such as union, intersection, difference, and subset. So, we implemented a very complete Set class compared to the current implementation of Set in other programming languages.

In the next chapter, we will cover hashes and dictionaries, which are non sequential data structures.