What are arrays?

Beginner Mar 25, 2019
Arrays are collections of data.

Before you read this article, we recommend that you read the What is a variable, What are loops and What are data-types articles.

In the What are loops article, we introduced the concept of having a "list" of people.

recipients = James, John, Jimmy, Jane, Jake, Jemma, Joanne, Juliet, Jessica, Josh

In most languages, this "list" would have been created using an array. An array is simply a collection of data.

An array is made up of elements. An element is an item within an array. In the above example, there are 10 elements (James is the first element, John is the second etc).

Syntactically an array is usually denoted using square brackets ([ and ]) with a comma separating each element. Arrays can hold any data-type.

Our list of recipients shows a list of names, which are Strings. To convert this list into an Array we would need to use quotation marks (") so they are interpreted as such.

recipients = ["James", "John", "Jimmy", "Jane", "Jake", "Jemma", "Joanne", "Juliet", "Jessica", "Josh"]

It's just as easy to create an Array with other data-types.

integers = [1,6,3,5,98]

floats = [2.4, 56.1, 46.1]

booleans = [true, true, false, true, false]

mixed = [5, true, 2.4, false, 3, 64.2]

Array elements have a corresponding number (index). This number is used to target specific elements. In most programming languages indexing starts at zero. Using our recipients example, this would look like the following:

recipients = ["James", "John", "Jimmy", "Jane", ... ]
index        |   0   |   1   |   2    |   3   | ...

As mentioned above, you can use the index to target specific elements in any order you want:

array[2] // => Jimmy

array[0] // => James

array[3] // => Jane

Photo by Glenn Carstens-Peters on Unsplash.