Click here to navigate the course.

Drag the edges to resize the window.

In Projects, you can keep track of your progress as you go throught the tasks. Check each item as you complete it!

Code Editor
Learn
Data Structures

Introduction to Hashes

We know that arrays are indexed with numbers that start with 0 and go up to the array's length minus one. (Think about it: an array with four elements has the indices 0, 1, 2, and 3.)

But what if we want to use numeric indices that don't go in order from 0 to the end of the array? What if we don't want to use numbers as indices at all? We'll need a new array structure called a hash.

Hashes are sort of like JavaScript objects or Python dictionaries. If you haven't studied those languages, all you need to know that a hash is a collection of key-value pairs. Hash syntax looks like this:

hash = { key1 => value1, key2 => value2, key3 => value3 }

Values are assigned to keys using =>. You can use any Ruby object for a key or value.

Instructions

We've created a hash in the editor to the right. See how it's made up of keys and values? Check out the code below it: it should look vaguely familiar. Click Run to see what it'll do!

Report a Bug
If you see a bug or any other issue with this page, please report it here.