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

Hash Tables for Speed

While hash tables are a perfect fit for paired data, they can also be used to make your code faster—even if your data doesn’t exist as pairs. And this is where things get exciting.

Here’s a simple array:

const array = [61, 30, 91, 11, 54, 38, 72];

If you want to search for a number in this array, how many steps would it take?

Because the array is unordered, you’d have to perform a linear search, which would take N steps—you learned this back at the beginning of the book.

However, what would happen if we ran some code that would convert these numbers into a hash table that looked like this?

const hashTable = {61: true, 30: true, 91: true,
11: true, 54: true, 38: true, 72: true}

Here, we’ve stored each ...