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Add properties to the class blueprint using the constructor method.
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Now that we have declared
the pet class and
0:00
created its constructor method,
let's outline what properties that
0:02
objects of this class type
will have available to them.
0:05
The object literals in the pets.js
file have three properties,
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animal, age, and breed.
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I think you'll agree that these
are appropriate to use in this pet
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class as well.
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If we were writing a Dog class instead,
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the animal property would be pretty
redundant, so we could leave that one out.
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But since we're writing a Pet class,
it's important to keep.
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To include a property in
a constructor method,
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you write the word this, followed by a
dot, followed by the name of the property.
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If you recall, when we want to add
a property to an object literal,
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the syntax is the name of the object
literal, followed by a dot, and
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then the new property.
0:44
We use this same pattern
in the constructor method,
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except instead of the object name,
we are using keyword this.
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That's because the this keyword
inside a constructor method
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is referring to the object
that is being created.
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The keyword this has different
meanings depending on where it's used,
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which is often confusing,
even to experienced JavaScript developers.
1:03
We don't get into the keyword
this too much in this course, but
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it's an important concept to know.
1:10
So I've included some links to other
Treehouse courses and workshops and
1:12
some outside documentation that can help
you understand this a little better.
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So to add the animal property,
we type this.animal.
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Now we have to set it equal to a value.
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But how do we know what to set it to?
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Later on, when we create
an instance of our Pet class, and
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this constructor method is invoked, we'll
pass it the value that we want to use.
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That means our constructor method
must be able to accept a parameter.
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To do that, inside the parentheses,
we type the word animal.
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Now we can set our animal
property equal to this parameter.
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Okay, let's add our other two properties,
and then we'll take a break.
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First, we'll add the parameters for
age and breed.
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Then just like we did for the animal
property, we'll create new properties for
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age and breed and
set them equal to the parameters.
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Wow, great job.
2:17
Congrats on completing your
very first constructor method.
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This is is amazing progress,
and I'm really proud of you.
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Let's take a break here to celebrate our
accomplishment, and when we come back,
2:25
we'll instantiate some pet objects and
start to see the fruits of our labor.
2:28
See you soon.
2:32
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