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Create a Multidimensional Array
5:32Create a program that uses a multidimensional array to hold songs and artists, and then displays a playlist of each song, with the artist who recorded it and the duration of the song.
All right, now let's create a program
that uses a multi-dimensional array
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to hold songs and artists, and
then displays a playlist of each song
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with the artist who recorded it and
the duration of the song.
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This is what the finished program
will display on the page.
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To code along with me,
open the file playlist-2.js, and
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in index.html, update the script
tag source attribute value
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to js/playlist-2.js.
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And while I'm here,
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I'm also going to change the text in
the heading back to My Music Playlist.
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The code in this playlist file is very
similar to the program you created in
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an earlier video where you
displayed a list of songs.
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Now you're also going to display the name
of the artist who performed the song and
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the song duration.
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I'll start by deleting all the string
values inside the playlist array.
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Then inside this array, add another array.
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Again, these square brackets
indicate an empty array literal.
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Now I have a two dimensional array,
or an array within an array.
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I'll add elements inside this array,
starting with a song name and a performer.
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I'll also add the length or
duration of the song as a string.
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So now I have an array containing
a nested array holding three elements.
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Next, I'll nest a second
array holding another song.
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I'll type a comma, square brackets,
and add three elements.
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Now I have an array,
playlist, with two elements.
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Each of those elements is
an array holding three items.
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I'll add the rest of the songs next.
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You can copy these arrays from
the teacher's notes with this video.
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Now that the multidimensional
array is complete,
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let's look at how you might
access some of its values.
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For example, I'll declare
a variable named myArtists and
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assign it a template literal.
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In the string,
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I want to display the artist's name
inside the first array, Miles Davis.
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playlist[0] points to the first
element of the playlist array.
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To display the artist name, I'll add
another set of brackets and access index
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position 1 of the nested array. I'll
display a couple of more artists.
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The artist in the second array,
with playlist[1][1],
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and the artist in the last array,
using playlist[5][1].
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Logging the value of the myArtists
variable to the console displays
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the three artists.
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Good.
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This was an example to get us
started accessing values in
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a multidimensional array.
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So I'll go ahead and
comment out this code, but
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feel free to take more time to
experiment with other index values.
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Next, to display the fully
formatted playlist on the page,
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I need to adjust the for
loop inside the createListItems function.
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Inside the loop, where we're accessing
an array element with arr[i],
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arr is the parameter name and represents
the array data passed into the function.
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That data is now a two dimensional array.
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So now,
i represents one of the nested arrays
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inside the playlist array
passed to this function.
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In other words, arr[0] points to this,
arr[1] to this, and so on.
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I want to access and
display each value of a nested array.
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So I need to add another set of brackets.
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To get to the song name, which is
the first element in the nested array,
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I'll type 0.
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For example,
now arr[0][0] points to So What,
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arr[1][0] points to Respect, and so on.
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To display the artist, I'll access
index position 1 of each array.
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For instance, arr[0][1] is Miles Davis.
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Within the template literal,
I'll add comma, by,
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and reference the array element that holds
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the artist's name with arr[i],
index position 1.
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Finally, I'll interpolate the song
duration value by referencing
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index position 2 of each
nested array with arr[i][2].
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Multidimensional arrays can
be a bit tricky at first, and
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there are other ways you might loop
through and access each array item.
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The key is to remember that to access
an element in a two dimensional array,
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like the playlist array, you use two
sets of square brackets, one for
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the outer array element and
one for the inner array element.
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All right, let's test this in the browser.
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l'll save the file, refresh the page, and
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there's the playlist displaying each song,
artist, and duration.
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Good.
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