Common array operations 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'

Apush

Bpop

Cunshift

Dshift

Attempts:

3 left

💡 Hint

Common Mistakes

Using pop instead of push removes the last element.

Using shift removes the first element instead of adding.

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

2fill in blank

medium

Complete the code to create a new array with each number doubled.

Javascript

const numbers = [1, 2, 3];
const doubled = numbers.[1](n => n * 2);
console.log(doubled);

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

Amap

Bfilter

Creduce

DforEach

Attempts:

3 left

💡 Hint

Common Mistakes

Using filter returns only elements that pass a test, not transformed elements.

Using forEach does not create a new array.

The map method creates a new array by applying a function to each element.

3fill in blank

hard

Fix the error in the code to find the first number greater than 10.

Javascript

const nums = [4, 9, 15, 7];
const first = nums.[1](n => n > 10);
console.log(first);

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

Areduce

Bfilter

Cmap

Dfind

Attempts:

3 left

💡 Hint

Common Mistakes

Using filter returns an array, not a single element.

Using map transforms all elements, not find one.

The find method returns the first element that matches the condition.

4fill in blank

hard

Fill both blanks to create an array of squares for numbers greater than 3.

Javascript

const nums = [1, 2, 3, 4, 5];
const squares = nums.[1](n => n > 3).[2](n => n * n);
console.log(squares);

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

Afilter

Bmap

Creduce

Dfind

Attempts:

3 left

💡 Hint

Common Mistakes

Using find instead of filter returns only one element.

Using reduce does not return an array.

First, filter selects numbers greater than 3, then map squares them.

5fill in blank

hard

Fill all three blanks to create an object counting occurrences of each fruit.

Javascript

const fruits = ['apple', 'banana', 'apple', 'orange', 'banana', 'apple'];
const count = fruits.[1]((acc, fruit) => {
  acc[[2]] = (acc[[3]] || 0) + 1;
  return acc;
}, {});
console.log(count);

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

Areduce

Bfruit

Dmap

Attempts:

3 left

💡 Hint

Common Mistakes

Using map instead of reduce does not accumulate counts.

Using different keys instead of fruit causes errors.

reduce builds an object counting each fruit. The key is the fruit name used twice.