What is TypeScript - Interactive Quiz & Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare a variable with a type in TypeScript.

Typescript

let age: [1] = 25;

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

Aboolean

Bstring

Cnumber

Dany

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'string' instead of 'number' for numeric values.

Omitting the type annotation.

In TypeScript, number is used to declare a variable that holds numeric values.

2fill in blank

medium

Complete the code to define a function that returns a string in TypeScript.

Typescript

function greet(): [1] {
  return "Hello!";
}

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

Avoid

Bboolean

Cnumber

Dstring

Attempts:

3 left

💡 Hint

Common Mistakes

Using void when the function returns a value.

Using number or boolean incorrectly.

The function returns a text, so its return type should be string.

3fill in blank

hard

Fix the error in the TypeScript interface declaration.

Typescript

interface Person {
  name: string;
  age: [1];
}

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

Astring

Bnumber

Cboolean

Dany

Attempts:

3 left

💡 Hint

Common Mistakes

Using string for numeric properties.

Leaving the type undefined.

The age property should be a number type because it holds numeric values.

4fill in blank

hard

Fill both blanks to create a typed array of strings in TypeScript.

Typescript

let fruits: [1] = ["apple", "banana", "cherry"]; // array of [2]

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

Astring[]

Bnumber[]

Cstring

Dboolean[]

Attempts:

3 left

💡 Hint

Common Mistakes

Using number[] or boolean[] for string arrays.

Confusing the array type with the element type.

The variable fruits is an array of strings, so the type is string[] and the comment describes the element type as string.

5fill in blank

hard

Fill all three blanks to create a typed object with optional and readonly properties in TypeScript.

Typescript

interface Car {
  readonly make: [1];
  model: [2];
  year?: [3];
}

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

Astring

Bnumber

Cboolean

Dany

Attempts:

3 left

💡 Hint

Common Mistakes

Using boolean for text or number properties.

Forgetting the optional property syntax.

The make and model are text values, so they use string. The year is a number and optional, so it uses number with a question mark.