Constructor parameter types in Typescript - Mini Project: Build & Apply

Constructor Parameter Types in TypeScript

📖 Scenario: You are creating a simple program to manage a library's book records. Each book has a title and a number of pages.

🎯 Goal: Build a TypeScript class Book that uses constructor parameter types to store the title and page count of a book.

📋 What You'll Learn

Create a class called Book

Add a constructor with parameters title (string) and pages (number)

Store the parameters as public properties

Create an instance of Book with title 'The Hobbit' and pages 310

Print the book's title and pages

💡 Why This Matters

🌍 Real World

Classes with typed constructor parameters are common in real-world TypeScript programs to model data clearly and safely.

💼 Career

Understanding constructor parameter types helps you write clean, maintainable code in professional TypeScript projects.

1

Create the Book class with constructor parameters

Create a class called Book with a constructor that has two parameters: title of type string and pages of type number. Store these parameters as public properties directly in the constructor.

Typescript

class Book {
  constructor(public title: string, public pages: number) {
    // Your code here
  }
}

Need a hint?

Use public before the constructor parameters to automatically create properties.

2

Create a Book instance

Create a variable called myBook and assign it a new Book object with the title 'The Hobbit' and pages 310.

Typescript

class Book {
  constructor(public title: string, public pages: number) {
  }
}

// Create an instance of Book
// Your code here

Need a hint?

Use new Book('The Hobbit', 310) to create the instance.

3

Access and print the book's properties

Use console.log to print the book's title and pages in the format: Title: The Hobbit, Pages: 310. Access the properties myBook.title and myBook.pages.

Typescript

class Book {
  constructor(public title: string, public pages: number) {
  }
}

const myBook = new Book('The Hobbit', 310);

// Print the book details
// Your code here

Need a hint?

Use a template string with backticks to format the output.

4

Run the program to see the output

Run the program to display the book's title and pages exactly as: Title: The Hobbit, Pages: 310.

Typescript

class Book {
  constructor(public title: string, public pages: number) {
  }
}

const myBook = new Book('The Hobbit', 310);

console.log(`Title: ${myBook.title}, Pages: ${myBook.pages}`);

// Run the program to see the output

Need a hint?

Check your console output matches exactly.