Readonly class properties in Typescript - Mini Project: Build & Apply

Readonly class properties

📖 Scenario: Imagine you are creating a program to manage books in a library. Each book has a title and an author. Once a book is created, its title and author should never change.

🎯 Goal: You will create a TypeScript class called Book with readonly properties title and author. Then, you will create an instance of this class and display its details.

📋 What You'll Learn

Create a class named Book with readonly properties title and author

Add a constructor to Book that sets title and author

Create an instance of Book with title 'The Great Gatsby' and author 'F. Scott Fitzgerald'

Print the book's title and author using console.log

💡 Why This Matters

🌍 Real World

Readonly properties are useful when you want to protect important data from being changed after creation, like book details, user IDs, or configuration settings.

💼 Career

Understanding readonly properties helps you write safer and more predictable TypeScript code, which is valuable in many software development jobs.

1

Create the Book class with readonly properties

Create a class called Book with readonly properties title and author of type string.

Typescript

class Book {
  // Your code here
}

Need a hint?

Use the readonly keyword before the property names to make them immutable.

2

Add a constructor to set the readonly properties

Add a constructor to the Book class that takes parameters title and author of type string and assigns them to the readonly properties.

Typescript

class Book {
  readonly title: string;
  readonly author: string;

  // Your code here
}

Need a hint?

The constructor sets the readonly properties when a new Book is created.

3

Create an instance of Book

Create a variable called myBook and assign it a new Book object with title 'The Great Gatsby' and author 'F. Scott Fitzgerald'.

Typescript

class Book {
  readonly title: string;
  readonly author: string;

  constructor(title: string, author: string) {
    this.title = title;
    this.author = author;
  }
}

// Your code here

Need a hint?

Use the new keyword to create an instance of the Book class.

4

Print the book's title and author

Use console.log to print the book's title and author from the myBook object in the format: Title: The Great Gatsby, Author: F. Scott Fitzgerald.

Typescript

class Book {
  readonly title: string;
  readonly author: string;

  constructor(title: string, author: string) {
    this.title = title;
    this.author = author;
  }
}

const myBook = new Book('The Great Gatsby', 'F. Scott Fitzgerald');

// Your code here

Need a hint?

Use a template string with backticks and ${} to insert the property values.