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You have completed Defining Variables with let and const!
You have completed Defining Variables with let and const!
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Using constants are a best practice when assigning variables but what happens when you do actually want to reassign a value? That's where let comes in.
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The let keyword is used when you
want to re-assign a variable.
0:00
In that respect, It just works like var.
0:04
Let's take a look at a simple example.
0:07
Open up let.html, and you can
see we've got the score = 0 and
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age = 33, and a boolean is hungry = false.
0:16
Open up the preview and
navigate to let.html.
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Open up the console, and
let's try and modify the score.
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The score can change through a game.
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The score increments by one each time
the player completes a challenge.
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Again, let just works like var.
0:43
You can reassign values to a variable
that is declared with the let keyword.
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You can update the age to be 34.
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And is hungry.
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To be true.
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Let's look at a more complex example where
you should use let rather than a const.
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Open up person.html, and
here we have a function called
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personDescription that
creates a description string.
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That gets logged out at the end here.
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If the person object has a role,
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it will add additional information at the
end of the description and is logged out.
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Let's see this in action.
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Go to the preview.
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Click on person.html,
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open up the developer console and
we should see Andrew is a teacher.
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If we change the var keyword in
the person description function to const.
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And run it again we get an error, because
we're trying to re-assign the description
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in the if block,
We could change it to var,
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or alternatively we could
use the new let keyword.
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Let works like var,
allowing you to re-assign variables, but
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unlike var, it has block level scoping.
2:23
We'll explore when we'd see the advantages
of using let over var in the next video.
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Now that we've changed the const to let,
let's see how it works in our browser.
2:32
Looking in the console, we see Andrew is
a teacher printed out like we expect.
2:38
In the next video,
2:42
we'll look at how let solved some problems
where the var keyword falls short.
2:43
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