Array creation in Javascript - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to create an empty array.

Javascript

const arr = [1];

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

A()

B{}

C[]

Dnull

Attempts:

3 left

💡 Hint

Common Mistakes

Using curly braces {} which create objects, not arrays.

Using parentheses () which are for function calls.

Using null which is not an array.

The correct way to create an empty array in JavaScript is using square brackets [].

2fill in blank

medium

Complete the code to create an array with three numbers: 1, 2, and 3.

Javascript

const numbers = [1];

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

A[1, 2, 3]

B(1, 2, 3)

C{1, 2, 3}

D1, 2, 3

Attempts:

3 left

💡 Hint

Common Mistakes

Using curly braces which create objects.

Using parentheses which are for grouping or function calls.

Listing values without brackets.

Arrays with elements are created using square brackets with values separated by commas.

3fill in blank

hard

Fix the error in the code to create an array with the string 'hello'.

Javascript

const greetings = [1];

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

A('hello')

B['hello']

C'hello'

D{'hello'}

Attempts:

3 left

💡 Hint

Common Mistakes

Using curly braces which create objects.

Using parentheses which do not create arrays.

Using just quotes which create a string, not an array.

Arrays must be created with square brackets. Curly braces create objects, parentheses group expressions, and quotes alone create strings.

4fill in blank

hard

Fill both blanks to create an array of squares for numbers 1 to 5.

Javascript

const squares = Array.from({length: 5}, (_, [1]) => ([2] + 1) * ([2] + 1));

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

Ai

Bindex

Cn

Dx

Attempts:

3 left

💡 Hint

Common Mistakes

Using different variable names for the index in the two blanks.

Using the first argument which is the element (undefined here).

The callback function receives the index as the second argument. Using index to represent it is clear and common. The square is calculated by multiplying (index + 1) by (index + 1).

5fill in blank

hard

Fill all three blanks to create an array of even numbers from 2 to 10.

Javascript

const evens = Array.from({length: [1], (_, [2]) => ([3] + 1) * 2);

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

A5

Bi

Cindex

Dn

Attempts:

3 left

💡 Hint

Common Mistakes

Using wrong length for the array.

Using the wrong variable name for the index.

Incorrect formula for even numbers.

The array length is 5 for numbers 2,4,6,8,10. The index variable is commonly named index. The formula uses (index + 1) * 2 to get even numbers starting from 2.