**Course Title:** Mastering TypeScript: From Basics to Advanced Applications **Section Title:** Modules and Namespaces **Topic:** Implement a TypeScript project that uses modules and namespaces. **Objective:** In this lab topic, we will implement a TypeScript project that uses modules and namespaces to demonstrate how to organize and structure large-scale applications. We will create a simple library management system that consists of multiple modules and namespaces to manage books, authors, and borrowers. **Project Structure:** Our project will contain the following modules and namespaces: * `book` module: will contain classes and interfaces for books * `author` module: will contain classes and interfaces for authors * `borrower` module: will contain classes and interfaces for borrowers * `library` module: will contain the main logic for managing the library * `utils` namespace: will contain utility functions for logging and validation **Step 1: Create a new TypeScript project** Create a new directory for our project and initialize a new TypeScript project using the following command: ```bash tsc --init ``` This will create a `tsconfig.json` file that we can use to configure our project. **Step 2: Create the `book` module** Create a new file called `book.ts` and add the following code: ```typescript // book.ts export interface Book { title: string; author: string; publicationDate: Date; } export class BookImpl implements Book { public title: string; public author: string; public publicationDate: Date; constructor(title: string, author: string, publicationDate: Date) { this.title = title; this.author = author; this.publicationDate = publicationDate; } } ``` This module defines an interface for books and a class that implements that interface. **Step 3: Create the `author` module** Create a new file called `author.ts` and add the following code: ```typescript // author.ts export interface Author { name: string; birthDate: Date; } export class AuthorImpl implements Author { public name: string; public birthDate: Date; constructor(name: string, birthDate: Date) { this.name = name; this.birthDate = birthDate; } } ``` This module defines an interface for authors and a class that implements that interface. **Step 4: Create the `borrower` module** Create a new file called `borrower.ts` and add the following code: ```typescript // borrower.ts export interface Borrower { name: string; libraryCardNumber: string; } export class BorrowerImpl implements Borrower { public name: string; public libraryCardNumber: string; constructor(name: string, libraryCardNumber: string) { this.name = name; this.libraryCardNumber = libraryCardNumber; } } ``` This module defines an interface for borrowers and a class that implements that interface. **Step 5: Create the `library` module** Create a new file called `library.ts` and add the following code: ```typescript // library.ts import { Book } from './book'; import { Author } from './author'; import { Borrower } from './borrower'; export class Library { private books: Book[]; private authors: Author[]; private borrowers: Borrower[]; constructor() { this.books = []; this.authors = []; this.borrowers = []; } addBook(book: Book) { this.books.push(book); } addAuthor(author: Author) { this.authors.push(author); } addBorrower(borrower: Borrower) { this.borrowers.push(borrower); } checkoutBook(book: Book, borrower: Borrower) { // implement checkout logic } returnBook(book: Book) { // implement return logic } } ``` This module defines a class that represents a library and has methods for adding books, authors, and borrowers, as well as checking out and returning books. **Step 6: Create the `utils` namespace** Create a new file called `utils.ts` and add the following code: ```typescript // utils.ts export namespace Utils { export function log(message: string) { console.log(message); } export function validateInput(input: string) { // implement validation logic } } ``` This namespace defines utility functions for logging and validation. **Step 7: Import and use the modules** Create a new file called `app.ts` and add the following code: ```typescript // app.ts import { Library } from './library'; import { Book } from './book'; import { Author } from './author'; import { Borrower } from './borrower'; import { Utils } from './utils'; const library = new Library(); const book = new BookImpl('The Great Gatsby', 'F. Scott Fitzgerald', new Date('1925-04-10')); library.addBook(book); const author = new AuthorImpl('F. Scott Fitzgerald', new Date('1896-09-24')); library.addAuthor(author); const borrower = new BorrowerImpl('John Doe', 'LIB1234'); library.addBorrower(borrower); library.checkoutBook(book, borrower); Utils.log('Book checked out!'); ``` This file imports and uses the modules we defined earlier to create a library, add books, authors, and borrowers, and check out a book. **Conclusion:** In this lab topic, we implemented a TypeScript project that uses modules and namespaces to demonstrate how to organize and structure large-scale applications. We created a simple library management system that consists of multiple modules and namespaces to manage books, authors, and borrowers. **Practice Exercise:** * Implement the checkout and return logic in the `library` module. * Add more functionality to the `library` module, such as searching for books by title or author. * Use the `Utils` namespace to log messages and validate input in the `library` module. **External Resources:** * TypeScript documentation: [https://www.typescriptlang.org/docs/](https://www.typescriptlang.org/docs/) * TypeScript GitHub repository: [https://github.com/microsoft/TypeScript](https://github.com/microsoft/TypeScript) * TypeScript Playground: [https://www.typescriptlang.org/play/](https://www.typescriptlang.org/play/) **Leave a comment:** If you have any questions or need help with this lab topic, leave a comment below.