Adding Properties Inside the Constructor Method

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, 0:09 animal, age, and breed. 0:14 I think you'll agree that these are appropriate to use in this pet 0:16 class as well. 0:19 If we were writing a Dog class instead, 0:21 the animal property would be pretty redundant, so we could leave that one out. 0:23 But since we're writing a Pet class, it's important to keep. 0:26 To include a property in a constructor method, 0:30 you write the word this, followed by a dot, followed by the name of the property. 0:32 If you recall, when we want to add a property to an object literal, 0:37 the syntax is the name of the object literal, followed by a dot, and 0:40 then the new property. 0:44 We use this same pattern in the constructor method, 0:46 except instead of the object name, we are using keyword this. 0:48 That's because the this keyword inside a constructor method 0:52 is referring to the object that is being created. 0:56 The keyword this has different meanings depending on where it's used, 0:59 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 1:07 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. 1:15 So to add the animal property, we type this.animal. 1:20 Now we have to set it equal to a value. 1:25 But how do we know what to set it to? 1:27 Later on, when we create an instance of our Pet class, and 1:29 this constructor method is invoked, we'll pass it the value that we want to use. 1:32 That means our constructor method must be able to accept a parameter. 1:37 To do that, inside the parentheses, we type the word animal. 1:40 Now we can set our animal property equal to this parameter. 1:47 Okay, let's add our other two properties, and then we'll take a break. 1:52 First, we'll add the parameters for age and breed. 1:56 Then just like we did for the animal property, we'll create new properties for 2:01 age and breed and set them equal to the parameters. 2:05 Wow, great job. 2:17 Congrats on completing your very first constructor method. 2:19 This is is amazing progress, and I'm really proud of you. 2:22 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