Heads up! To view this whole video, sign in with your Courses account or enroll in your free 7-day trial. Sign In Enroll
Preview
Start a free Courses trial
to watch this video
Learn how to create and work with arrays that contain other arrays, or "multidimensional arrays".
Resources
Related Discussions
Have questions about this video? Start a discussion with the community and Treehouse staff.
Sign upRelated Discussions
Have questions about this video? Start a discussion with the community and Treehouse staff.
Sign up
[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
You need to sign up for Treehouse in order to download course files.
Sign upYou need to sign up for Treehouse in order to set up Workspace
Sign up