A Common-Sense Guide to Data Structures and Algorithms in JavaScript, Volume 1

Hash Tables

Most programming languages include a data structure called a hash table, and it has an amazing superpower: fast reading. Note that hash tables are called by different names in various programming languages. In JavaScript they’re called objects, and other languages call them hashes, maps, hash maps, dictionaries, or associative arrays. We’ll refer to them as hash tables since that’s a common universal way to refer to this data structure.

Here’s an example of the menu as implemented with a hash table:

const menu = { "french fries": 0.75, "hamburger": 2.5,
"hot dog": 1.5, "soda": 0.6 };

A hash table is a list of paired values. The first item in each pair is called the key, and the second item is called the value. In a hash ...