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We'll look at two "if..then" statements in this video to remind ourselves how they work. In the videos that follow, we'll see how to reform these statements into different conditional patterns.
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[MUSIC]
0:00
Hello there, Andrew here.
0:04
JavaScript developer, lifelong learner,
and teacher here at Treehouse.
0:05
I'd like to show you a few ways
to represent decisions in your
0:10
JavaScript code.
0:14
You've already learned how to write an if,
0:16
else statement, to choose between
one scenario and another.
0:18
This is called a conditional because it
does one thing if a condition is true and
0:22
something else if it isn't.
0:26
The paths that's an if, else statement
follows are called branches.
0:29
They branch the flow of your programs
logic in different directions
0:34
based on the results
of a conditional test.
0:39
You can branch off in as
many directions as you want.
0:42
Let's look at two examples of branching,
using if statements.
0:46
A two way and a multi way conditional.
0:50
We'll meet them in different ways later.
0:53
First let's look at a very simple
example of if, else statements.
0:57
If you'd like to follow along, open up the
workspace with this video or if you prefer
1:02
to use your own text editor, download
the project files with this video.
1:07
I have a file named two.js, which is
a simple example of two way branching.
1:11
I have another file named multi.js,
with multi-way branching.
1:19
And another file short_circuit.js,
with no code in right now.
1:24
I'll run these in node but
1:31
everything I'll show you in this
workshop will work in the browser too.
1:32
In two.js, you see that I have a variable
named is true which is set to true.
1:37
If the variable contains a true
value the console prints yes,
1:44
if the value is false
the console prints no.
1:50
Let's run this by typing node two.js and
we see that yes it's printed.
1:56
Now if we change is true to false and
2:05
we rerun it we see no.
2:11
Let's take a look at multi.js now,
we have a multi-way branch here.
2:15
If the day value is zero, then the
console prints the string Sunday.
2:23
If it's one, Monday.
2:30
Two, Tuesday.
2:33
And so on.
2:37
If it's not a number between zero and
2:38
six invalid day will be
printed to the console.
2:40
Let's see this in action.
2:45
Day is set to 1 now.
2:47
So when we type in node multi.js,
Monday appears.
2:49
Let's change it to four and re-run it.
2:57
We see Thursday.
3:02
If we change it to new Date().getDay()
3:04
you should see today's day.
3:10
This may not be quite accurate
if you're using workspaces
3:15
depending on the number of time zones
between you and Treehouse servers.
3:19
If you run this locally on your computer
you should get the correct day there.
3:23
Let's see our default case now.
3:28
Set day to 8.
3:30
And run the script.
3:35
We see Invalid Day.
3:37
Great.
3:41
We'll come back to these examples
in the following videos and
3:42
rewrite them with different
conditional statements.
3:45
The conditional statements
we'll look at in this workshop
3:48
aren't necessarily considered
best practices, but
3:51
you will see these pop up in stack
overflow, tech blogs and other code bases.
3:54
So it's good to know about
them understand them.
4:00
Our first stop on this tour is
to visit the switch statement,
4:03
a very compact way of adding multiple
branching logic to a program.
4:06
I will see you there
4:10
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