Data Structures and Algorithms with JavaScript

Chapter 7. Dictionaries

A dictionary is a data structure that stores data as key-value pairs, such as the way a phone book stores its data as names and phone numbers. When you look for a phone number, you first search for the name, and when you find the name, the phone number is found right next to the name. The key is the element you use to perform a search, and the value is the result of the search.

The JavaScript Object class is designed to operate as a dictionary. In this chapter we’ll use the features of the Object class to build a Dictionary class that simplifies working with a dictionary-type object. You can perform the same functions shown in this chapter using just JavaScript arrays and objects, but creating a Dictionary class makes doing the work easier and more fun. For example, it’s a lot easier to use () to reference keys rather than having to use [] notation. There is also, of course, the advantage of being able to define functions for performing collective operations, such as displaying all entries in a dictionary, rather than having to write loops in the main program to perform the same operations.

The Dictionary Class

The basis for the Dictionary class is an Object, but using Array access notation, since objects in JavaScript are associative arrays.. This approach allows us to dynamically add key-value pairs, and use Array functionality such as sorting, but at the same time, allowing us to have string keys rather than just numeric.

We’ll start our definition ...