Lesson 2

Bringing Classes to Life: Attributes and Methods in JavaScript

Lesson Overview

Hello there! Today, we're diving into JavaScript classes, focusing on attributes and methods. Attributes are characteristics, whereas methods define behaviors. You'll learn these concepts through a Dog class. By the end of the lesson, you should be able to use attributes and methods in JavaScript classes effectively.

Understanding Attributes in JavaScript Classes

Think of attributes as properties. For a Dog class, the attributes might include name: "Fido", breed: "Poodle", color: "White". These attributes describe the characteristics of a dog like Fido.

Creating Attributes in a JavaScript Class

We add attributes to the class constructor. Below, we're setting the name, breed, and color for the Dog class:

1class Dog { 2 name = 'Fido'; 3 breed = 'Poodle'; 4 color = 'White'; 5}

When we create an instance:

1const fido = new Dog(); 2console.log(fido.name); // Prints: Fido 3console.log(fido.breed); // Prints: Poodle 4console.log(fido.color); // Prints: White

We see Fido, an object of the Dog class.

Understanding Methods in JavaScript Classes

Methods are actions that instances of a class can perform. For the Dog class, behaviors might include bark(), eat(), and sleep(). Methods are functions defined within the class.

Creating Methods in a JavaScript Class

Let's make Fido more interesting with some activities. We can give him actions like barking, eating, and sleeping by adding methods to the 'Dog' class.

1class Dog { 2 name = 'Fido'; 3 breed = 'Poodle'; 4 color = 'White'; 5 6 bark() { 7 console.log(`Woof Woof!`); 8 } 9 10 eat(food) { 11 // "this" corresponds to the reference to the current Dog class instance 12 console.log(`${this.name} is eating ${food}.`); 13 } 14 15 sleep() { 16 console.log(`Zzz...`); 17 } 18}

Here, bark, eat, and sleep methods define the behavior of a Dog object. A particular instance of Dog can now bark, eat, and sleep. Note the use of this in the eat(food) method - this way we reference the class attribute, where this corresponds to the reference to the current instance of the Dog class.

Using Attributes and Methods in JavaScript Class Instances

Let's create an instance of the Dog class and call its methods:

1const fido = new Dog(); 2 3console.log(fido.name); // Prints: Fido 4console.log(fido.breed); // Prints: Poodle 5console.log(fido.color); // Prints: White 6 7fido.bark(); // Prints: Woof Woof! 8fido.eat("bone"); // Prints: Fido is eating bone. 9fido.sleep(); // Prints: Zzz...

With the use of attributes and methods, we've been able to bring our Dog class to life.

Lesson Summary and Practice

That's it! With attributes and methods, you can make JavaScript classes more interactive. In this lesson, using the Dog class, we've added and used attributes and methods. Up next are some exercises for you to practice and master these concepts. Happy coding!

Enjoy this lesson? Now it's time to practice with Cosmo!

Practice is how you turn knowledge into actual skills.