Adding Behavior With Methods

Learning Goals

• Write methods that use instance data and parameter data

Introduction

In review, with Object-Oriented programming (OOP), we can use classes to represent concepts such as students, books, comments, posts, or even animals.

We should only have to define the properties and methods of a class once. Different instances of this class will all have the same properties and methods. Specific values for those properties will be different between instances. Mickey and Minnie are both Mouse instances that have a property called name, but the value of that property for each is different.

With knowledge of constructors, we can use JavaScript's classes as a template for instances.

Write a Method That Uses Instance Data and Parameter Data

To practice OOP concepts, let's create 3 classes that use constructor methods. These constructors will assign properties based on initial parameters. We'll also write methods that leverage these properties.

1. Create classes Cat, Dog, and Bird
2. Each of these classes will accept the parameters name and sex and will store those values as properties.

class Cat {
  //...
}

class Dog {
  //...
}

class Bird {
  //...
}

For each class, create the method speak.

• For an instance of Cat, speak returns "name says meow!",
• For an instance of Dog, speak returns "name says woof!"
• For an instance of Bird, speak returns conditional output. If the instance of Bird is male, speak returns "It's me! name, the parrot!". If it is not male, speak returns "name says squawk!".

Conclusion

We've learned to instantiate class instances, or "objects" in JavaScript. The constructor function allows us to easily define and standardize the instances we create. Good work!

Resources

• Mozilla Developer Network - this
• JavaScript — Multiple Ways to Create Objects