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