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JavaScript Arrays

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What is a Multidimensional Array?

3:29 with Guil Hernandez

Learn how to create and work with arrays that contain other arrays, or "multidimensional arrays".

[MUSIC] 0:00
Arrays can contain strings, numbers, Booleans, and other types. 0:09
Arrays can also hold any combination of values. 0:14
For example, an array might have the string Hello in the first position, 0:17
the number 23 in the second, and the value true in the third position. 0:22
In fact, you can place an array within an array, 0:26
even create an array that contains nothing but other arrays. 0:29
An array inside an array is called a multidimensional or two dimensional array. 0:33
That might sound a bit strange and confusing right now, but you can start to 0:38
think of a multidimensional array as a list containing other lists. 0:43
You can picture a two-dimensional array as a spreadsheet. 0:46
Think of the spreadsheet as the master list, a list containing other lists. 0:50
The data in the spreadsheet is organized into rows and columns. 0:55
Each row represents one array or one of the arrays inside the master array. 0:59
And each column cell represents one element in an array. 1:04
For example, you might use an array to store the grades of multiple students. 1:08
Let's say three students took four tests. 1:13
Each row represents one student, and each column is one test score. 1:16
For instance, the first row represents Student 1, and 1:21
their test scores are 80, 90, 100, and 95. 1:25
The second student's scores appear in the second row, and 1:29
their scores are 75, 95, 85, and 100. 1:33
The third student's test scores are in the last row. 1:37
You've probably seen data like this in a spreadsheet. 1:40
So what would this look like as a multidimensional array in JavaScript? 1:43
You start by creating an array, then at elements inside the array, 1:47
each element is another array. 1:51
You'd add the first student's grades like this. 1:54
Notice that there's another set of square brackets, 1:57
which indicates that there's an array nested inside the array. 2:00
You add the next set of student grades by adding a comma and another array. 2:03
Another comma and another nested array adds the last student's grades. 2:08
Now, how do you access these different sets of grades? 2:12
First, let's start with how you get the grades for an individual student. 2:15
Since each set of student grades is one element in the grades array, 2:20
you use the index notation you learned about earlier. 2:25
For example, the first student's grades are at grades[0], 2:28
the first element in the grades array. 2:31
The second student's grades are in the second element, at index position 1. 2:34
And the third student's grades are at grades[2]. 2:38
Because each of those index values represents another array, 2:42
you can access an element in a nested array using another index value. 2:46
For example, 2:51
the first array of student grades is that index position 0 of the outer array. 2:51
To access the last grade in that first nested array, chain a second 2:57
set of square brackets holding the index value of the last element, like this. 3:02
Now, how would you get to the first grade of the last student? 3:07
Well, that grade is in the last nested array, which is at index 2 and 3:10
position 0 of that array. 3:14
This example uses arrays of numbers to represent student grades. 3:17
But you can create a multidimensional array containing lists of any value, 3:21
strings, numbers and Booleans, for instance. 3:25