Namespace declaration in Typescript - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of accessing nested namespace value

What is the output of this TypeScript code using namespaces?

Typescript

namespace Outer {
  export namespace Inner {
    export const value = 42;
  }
}
console.log(Outer.Inner.value);

A 42

B undefined

C ReferenceError

D null

💡 Hint

Remember that exported members inside nested namespaces can be accessed using dot notation.

The value 42 is exported inside the nested namespace Inner, which is inside Outer. Accessing Outer.Inner.value prints 42.

🧠 Conceptual

intermediate

Purpose of 'export' keyword in namespaces

In TypeScript namespaces, what does the 'export' keyword do?

A Deletes the member after compilation

B Makes the member accessible outside the namespace

C Automatically imports the member into other namespaces

D Prevents the member from being accessed outside the namespace

💡 Hint

Think about how you can use a variable or function declared inside a namespace from outside it.

The 'export' keyword allows members inside a namespace to be accessed from outside that namespace.

🔧 Debug

advanced

Identify the error in namespace usage

What error will this TypeScript code produce?

Typescript

namespace MySpace {
  const secret = 'hidden';
}
console.log(MySpace.secret);

A Property 'secret' does not exist on type 'typeof MySpace'.

B ReferenceError: secret is not defined

C SyntaxError: Unexpected token

D No error, outputs 'hidden'

💡 Hint

Check if the member is exported to be accessible outside the namespace.

Since 'secret' is not exported, it is not accessible outside the namespace, causing a property error.

📝 Syntax

advanced

Correct syntax to declare a namespace with a function

Which option correctly declares a namespace with an exported function named greet?

A namespace GreetSpace { export greet() { return 'Hello'; } }

B namespace GreetSpace { function greet() { return 'Hello'; } }

C namespace GreetSpace { export function greet() { return 'Hello'; } }

D namespace GreetSpace { export const greet = () => 'Hello'; }

💡 Hint

Remember the correct syntax for exporting a function inside a namespace.

Option C correctly uses 'export function' syntax. Option C misses export, C has invalid syntax, D uses const which is valid but not the exact function declaration asked.

🚀 Application

expert

Number of accessible members after merging namespaces

Given these two namespace declarations, how many members are accessible from outside under the merged namespace 'Tools'?

Typescript

namespace Tools {
  export function toolA() { return 'A'; }
}
namespace Tools {
  export function toolB() { return 'B'; }
  function hiddenTool() { return 'hidden'; }
}
// Outside the namespace
const count = Object.keys(Tools).length;

A 0

B 3

C 1

D 2

💡 Hint

Only exported members are accessible outside. Hidden functions are not counted.

The merged namespace 'Tools' has two exported functions: toolA and toolB. The hiddenTool is not exported, so only 2 members are accessible.