Dictionaries and Hashes

In the previous chapter, we learned about sets. In this chapter, we will continue our discussion about data structures that store unique values (non-repeated values) using dictionaries and hashes.

In a set, we are interested in the value itself as the primary element. In a dictionary (or map), we store values in pairs as [key, value]. The same goes for hashes (they store values in pairs, such as [key, value]); however, the way that we implement these data structures is a little bit different as dictionaries can only store a single value per key, as we will learn in this chapter.

In this chapter, we will cover:

• The dictionary data structure
• The hash table data structure
• Handling collisions in hash tables
• The ECMAScript 2015 Map, WeakMap, and WeakSet classes