Why TypeScript over JavaScript - Test Your Understanding

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'

Avar

Blet

Cstring

Dnumber

Attempts:

3 left

💡 Hint

Common Mistakes

Using JavaScript keywords like 'var' or 'let' as types.

Using 'string' when the value is a number.

In TypeScript, you specify the type after the colon. Here, number is the correct type for the variable age.

2fill in blank

medium

Complete the code to define a function parameter type in TypeScript.

Typescript

function greet(name: [1]) { console.log(`Hello, ${name}!`); }

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

Anumber

Bstring

Cboolean

Dany

Attempts:

3 left

💡 Hint

Common Mistakes

Using number or boolean for text data.

Using any without reason.

The parameter name should be a string because it represents text.

3fill in blank

hard

Fix the error by completing the type annotation for the array.

Typescript

let scores: [1] = [10, 20, 30];

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

Anumber[]

Bany

Cboolean[]

Dstring[]

Attempts:

3 left

💡 Hint

Common Mistakes

Using string[] when the array has numbers.

Using boolean[] incorrectly.

The array scores contains numbers, so its type is number[].

4fill in blank

hard

Fill in the blank to create a typed object in TypeScript.

Typescript

let person: [1] = { name: 'Alice', age: 30 };

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

Aany

B{ name: number; age: string }

C{ name: string; age: number }

Dobject

Attempts:

3 left

💡 Hint

Common Mistakes

Swapping the types of name and age.

Using any or object without specific types.

The object person has a name as a string and age as a number, so the type annotation matches that structure.

5fill in blank

hard

Fill all three blanks to create a typed function with parameters and return type.

Typescript

function add(a: [1], b: [2]): [3] { return a + b; }

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

Astring

Bnumber

Dboolean

Attempts:

3 left

💡 Hint

Common Mistakes

Using string types for parameters or return value.

Using boolean as a type here.

The function add takes two numbers and returns a number, so the parameter types and return type are number.