Declaration merging for namespaces in Typescript - Mini Project: Build & Apply

Declaration merging for namespaces

📖 Scenario: Imagine you are organizing a library system. You want to group related information about books and authors using namespaces. Sometimes, you need to add more details to the same namespace without rewriting it.

🎯 Goal: You will create two separate namespace declarations with the same name and see how TypeScript merges them into one. This helps keep your code organized and extendable.

📋 What You'll Learn

Create a namespace called Library with a function getBookTitle that returns a string.

Add a second Library namespace with a function getAuthorName that returns a string.

Call both functions and print their results to see the merged namespace in action.

💡 Why This Matters

🌍 Real World

In large projects, you often want to split code into parts but keep related things grouped. Declaration merging lets you add to the same namespace from different files or sections.

💼 Career

Understanding declaration merging helps you maintain and extend TypeScript codebases, especially when working with libraries or modular code.

1

Create the first Library namespace

Create a namespace called Library with a function getBookTitle that returns the string "The Great Gatsby".

Typescript

// Your code here

Need a hint?

Use namespace Library { export function getBookTitle() { return "The Great Gatsby"; } }

2

Add a second Library namespace

Add another namespace called Library with a function getAuthorName that returns the string "F. Scott Fitzgerald".

Typescript

namespace Library {
    export function getBookTitle(): string {
        return "The Great Gatsby";
    }
}

// Your code here

Need a hint?

Write a second namespace Library block with the new function inside.

3

Call both functions from the merged Library namespace

Write code to call Library.getBookTitle() and Library.getAuthorName(), storing their results in variables title and author.

Typescript

namespace Library {
    export function getBookTitle(): string {
        return "The Great Gatsby";
    }
}

namespace Library {
    export function getAuthorName(): string {
        return "F. Scott Fitzgerald";
    }
}

// Your code here

Need a hint?

Use const title = Library.getBookTitle(); and const author = Library.getAuthorName();

4

Print the results

Print the variables title and author using two separate console.log statements.

Typescript

namespace Library {
    export function getBookTitle(): string {
        return "The Great Gatsby";
    }
}

namespace Library {
    export function getAuthorName(): string {
        return "F. Scott Fitzgerald";
    }
}

const title = Library.getBookTitle();
const author = Library.getAuthorName();

// Your code here

Need a hint?

Use console.log(title); and console.log(author); to show the results.