Modifying arrays in Javascript - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to add an element to the end of the array.

Javascript

const fruits = ['apple', 'banana'];
fruits.[1]('orange');
console.log(fruits);

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

Aunshift

Bpop

Cpush

Dshift

Attempts:

3 left

💡 Hint

Common Mistakes

Using pop instead of push removes the last item.

Using shift or unshift changes the start of the array.

The push method adds an element to the end of an array.

2fill in blank

medium

Complete the code to remove the first element from the array.

Javascript

const numbers = [10, 20, 30];
numbers.[1]();
console.log(numbers);

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

Ashift

Bpush

Cpop

Dunshift

Attempts:

3 left

💡 Hint

Common Mistakes

Using pop removes the last element, not the first.

Using push or unshift adds elements instead of removing.

The shift method removes the first element from an array.

3fill in blank

hard

Fix the error in the code to replace the second element with 'grape'.

Javascript

const fruits = ['apple', 'banana', 'cherry'];
fruits[[1]] = 'grape';
console.log(fruits);

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

A'2'

B2

C'1'

D1

Attempts:

3 left

💡 Hint

Common Mistakes

Using index 2 changes the third element, not the second.

Using string indexes causes errors.

Array indexes start at 0, so the second element is at index 1.

4fill in blank

hard

Fill both blanks to create a new array with squares of even numbers only.

Javascript

const numbers = [1, 2, 3, 4, 5];
const squares = numbers.filter(n => n [1] 2 === 0).map(n => n [2] 2);
console.log(squares);

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

A%

B**

C===

D+

Attempts:

3 left

💡 Hint

Common Mistakes

Using '+' instead of '**' adds numbers instead of squaring.

Using '===' in filter instead of '%' causes wrong filtering.

The filter uses % 2 === 0 to find even numbers. The map uses ** 2 to square them.

5fill in blank

hard

Fill all three blanks to create an object mapping words to their lengths, only for words longer than 3 letters.

Javascript

const words = ['cat', 'elephant', 'dog', 'lion'];
const lengths = {};
for (let index [3] words) {
  const word = words[index];
  if (word.length > 3) {
    lengths[[1]] = [2];
  }
}
console.log(lengths);

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

Aword

Bword.length

Cfor

Din

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'for' instead of 'in' in the loop causes syntax errors.

Using 'for' as a key or value is incorrect.

This uses a for...in loop to iterate over array indexes and map words to their lengths if longer than 3 letters.