As you have learned, a set is a collection of distinct elements (non-repeated elements). A dictionary is used to store [key, value] pairs, where the key is used to find a particular element. The dictionary is very similar to a set; a set stores a [key, key] collection of elements, and a dictionary stores a [key, value] collection of elements. A dictionary is also known as a map.
In this chapter, we will cover some examples of the use of the dictionary data structure in the real world: a dictionary itself (the words and their definitions), and an address book.
Similar to the Set class, ECMAScript 6 also contains an implementation of the Map class—also known as a dictionary.
Note
You can check out the details of the ECMAScript 6 Map class implementation at https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Map (or http://goo.gl/dm8VP6).
The class we are going to implement in this chapter is based on the Map implementation of ECMAScript...