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Properties and Methods

Part of the Object Oriented Programming section of Coddy's JavaScript journey. Lesson 13 of 56.

Classes in JavaScript allow us to define properties and methods that will be shared by all instances of the class.

Create a class with properties:

class Car {
  constructor(make, model) {
    this.make = make;
    this.model = model;
  }
}

When creating an instance, the constructor sets these properties:

const myCar = new Car('Toyota', 'Corolla');
console.log(myCar.make);  // Output: 'Toyota'
console.log(myCar.model); // Output: 'Corolla'

Add a method to the class:

class Car {
  constructor(make, model) {
    this.make = make;
    this.model = model;
  }
  
  getDescription() {
    return `This car is a ${this.make} ${this.model}.`;
  }
}

Now we can call this method on any instance:

const myCar = new Car('Toyota', 'Corolla');
console.log(myCar.getDescription()); // Output: 'This car is a Toyota Corolla.'

Challenge

Create a class named Book in the book.js file with the following:

A constructor that takes title, author, and pages parameters and sets them as properties.
A method called getInfo that returns a string in the format: “Title: [title], Author: [author], Pages: [pages]”
Export the class by adding `export` in front of the `class` declaration

Try it yourself

import { Book } from './book.js';

// Test (do not modify this part)
const book = new Book("JavaScript Basics", "John Doe", 200);
console.log(book.getInfo());

Test yourself

This lesson includes a short quiz. Start the lesson to answer it and track your progress.

All lessons in Object Oriented Programming

1Objects & The this Keyword

Quick Review: Objects Adding Methods to Objects Understanding the this Keyword Constructor Functions The new Keyword Recap Challenge

4Methods & Managing State

Methods that modify state Method chaining pattern

7 Inheritance & The extends Key

Inheritance The "is-a" Relationship The extends Keyword The super() Method Inheriting Properties&Methods Recap Challenge

10Polymorphism

What is Polymorphism?Overriding Inherited Methods Using super Recap Challenge

13Composition vs. Inheritance

The "has-a" vs. "is-a"The Limits of Deep Inheritance Building objects

2Organizing Code

What are Modules?Exporting with export Importing with import Default vs. Named Exports

5Encapsulation & Access

Encapsulation Public & Private Class Fields Private Methods Recap Challenge

8Organizing OOP Code

Organize Classes into Modules

11Project: A Shape Renderer

Setup: Shape Class & Export Circle Class Inheritance Overriding & Area Method Static Shape Counter

14Library Management System

Designing the Library Book Class with Composition Book Author Validation

3Classes & Objects

What is a Class?Creating InstancesProperties and MethodsRecap Challenge

6Project: A Simple Bank Account

BankAccount Class Deposits and Withdrawals Balance as Private Field

9Static Methods & Properties

Class-Level vs. Instance-Level Static Properties Static Utility Methods Recap challenge

12Getters & Setters

The get and set Keywords Computed Properties Validation and Side Effects Recap Challenge

15 Final Challenges

Game Character Builder E-commerce Product System University Management System Smart Home Device System

Practice on your own: Online JavaScript compiler