Namespace declaration in Typescript - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare a namespace named MyNamespace.

Typescript

namespace [1] {
  export const greeting = "Hello";
}

Drag options to blanks, or click blank then click option'

ANamespace

BMyNamespace

CmyNamespace

DNamespace1

Attempts:

3 left

💡 Hint

Common Mistakes

Using lowercase or different casing for the namespace name.

Using reserved words like 'Namespace' as the name.

The keyword namespace is followed by the exact name of the namespace, which is MyNamespace here.

2fill in blank

medium

Complete the code to access the greeting constant inside the MyNamespace namespace.

Typescript

console.log([1].greeting);

Drag options to blanks, or click blank then click option'

AGreeting

Bnamespace

CMyNamespace

DmyNamespace

Attempts:

3 left

💡 Hint

Common Mistakes

Using incorrect casing for the namespace name.

Trying to access the member without the namespace prefix.

To access a member inside a namespace, use the namespace name followed by a dot and the member name.

3fill in blank

hard

Fix the error in the namespace declaration by completing the code.

Typescript

namespace [1] {
  export function greet() {
    return "Hi!";
  }
}

Drag options to blanks, or click blank then click option'

AMyNamespace

Bnamespace

CmyNamespace

DGreetNamespace

Attempts:

3 left

💡 Hint

Common Mistakes

Using reserved words as namespace names.

Using inconsistent casing.

Namespace names should be valid identifiers and follow the naming convention used in the rest of the code.

4fill in blank

hard

Fill both blanks to declare a namespace Utils with a constant version set to 1.0.

Typescript

namespace [1] {
  export const [2] = 1.0;
}

Drag options to blanks, or click blank then click option'

AUtils

BVersion

Cversion

Dutils

Attempts:

3 left

💡 Hint

Common Mistakes

Using uppercase for the constant name.

Using lowercase for the namespace name.

The namespace name is Utils and the constant inside is named version with lowercase 'v'.

5fill in blank

hard

Fill all three blanks to declare a namespace MathOps with a function add that returns the sum of two numbers a and b.

Typescript

namespace [1] {
  export function [2](a: number, b: number): number {
    return a [3] b;
  }
}

Drag options to blanks, or click blank then click option'

AMathOps

Badd

C+

Dsubtract

Attempts:

3 left

💡 Hint

Common Mistakes

Using the wrong operator like '-' instead of '+'.

Naming the function incorrectly.

The namespace is MathOps, the function is named add, and the operator for addition is +.

Practice

1. What is the main purpose of a namespace in TypeScript?

easy

A. To import external libraries

B. To create a new type of variable

C. To define a function that runs automatically

D. To group related code under one name and avoid name clashes

Solution

1. Step 1: Understand what namespaces do

   Namespaces group related code together to keep it organized.

2. Step 2: Recognize the benefit of namespaces

   They help avoid name clashes by keeping code under one name.

3. Final Answer:

   To group related code under one name and avoid name clashes -> Option D

4. Quick Check:

   Namespaces = Group code + avoid clashes [OK]

Hint: Namespaces group code to avoid name conflicts [OK]

Common Mistakes:

• Thinking namespaces create new variable types
• Confusing namespaces with functions
• Assuming namespaces import libraries

2. Which of the following is the correct syntax to declare a namespace named Utils in TypeScript?

easy

A. namespace Utils { }

B. module Utils { }

C. package Utils { }

D. namespace = Utils { }

Solution

1. Step 1: Recall the correct keyword for namespaces

   TypeScript uses the keyword namespace to declare namespaces.

2. Step 2: Check the syntax format

   The correct syntax is namespace Name { }, so namespace Utils { } is correct.

3. Final Answer:

   namespace Utils { } -> Option A

4. Quick Check:

   Namespace syntax = namespace Name { } [OK]

Hint: Use 'namespace Name { }' to declare namespaces [OK]

Common Mistakes:

• Using 'module' instead of 'namespace'
• Adding '=' sign in declaration
• Using 'package' keyword which is invalid

3. What will be the output of the following TypeScript code?

namespace MathOps {
  export function add(a: number, b: number) {
    return a + b;
  }
}

console.log(MathOps.add(3, 4));

medium

A. undefined

B. 7

C. Error: add is not defined

D. NaN

Solution

1. Step 1: Understand the namespace and export usage

   The function add is inside namespace MathOps and is exported, so it can be accessed outside.

2. Step 2: Evaluate the function call

   Calling MathOps.add(3, 4) returns 3 + 4 = 7.

3. Final Answer:

   7 -> Option B

4. Quick Check:

   Exported function call returns sum 7 [OK]

Hint: Exported namespace members are accessible outside [OK]

Common Mistakes:

• Forgetting to export the function
• Trying to call function without namespace prefix
• Expecting runtime errors due to namespace

4. Identify the error in this TypeScript namespace code:

namespace Data {
  function getData() {
    return "info";
  }
}

console.log(Data.getData());

medium

A. Function getData is not exported, so it cannot be accessed outside

B. Namespace name Data is invalid

C. Syntax error in namespace declaration

D. Console.log is misspelled

Solution

1. Step 1: Check function accessibility inside namespace

   The function getData is declared but not exported, so it's private to the namespace.

2. Step 2: Understand why console.log(Data.getData()) fails

   Since getData is not exported, it cannot be accessed outside the namespace, causing an error.

3. Final Answer:

   Function getData is not exported, so it cannot be accessed outside -> Option A

4. Quick Check:

   Export missing = access error [OK]

Hint: Export functions to access them outside namespaces [OK]

Common Mistakes:

• Assuming all namespace members are public by default
• Thinking namespace name is invalid
• Ignoring export keyword importance

5. Given two namespaces below, what is the correct way to call the log function from Logger inside App?

namespace Logger {
  export function log(message: string) {
    console.log("LOG: " + message);
  }
}

namespace App {
  export function run() {
    // Call Logger.log here
  }
}

App.run();

hard

A. log("App started");

B. App.Logger.log("App started");

C. Logger.log("App started");

D. Logger::log("App started");

Solution

1. Step 1: Understand namespace access rules

   Namespaces are accessed by their name followed by dot and member name, so Logger.log is correct.

2. Step 2: Check the options for calling the function

   Only Logger.log("App started") correctly calls the exported function from the Logger namespace.

3. Final Answer:

   Logger.log("App started"); -> Option C

4. Quick Check:

   Namespace function call = NamespaceName.member [OK]

Hint: Call namespace functions with NamespaceName.function() [OK]

Common Mistakes:

• Calling function without namespace prefix
• Using invalid syntax like '::'
• Assuming nested namespaces auto-import members