Iterating over arrays in Javascript - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to loop through the array and print each number.

Javascript

const numbers = [1, 2, 3, 4];
for (let [1] = 0; [1] < numbers.length; [1]++) {
  console.log(numbers[[1]]);
}

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

Ai

Bnum

Cindex

Ditem

Attempts:

3 left

💡 Hint

Common Mistakes

Using a variable name that is not consistent throughout the loop.

Starting the loop counter at 1 instead of 0.

We use i as the loop counter variable to access each index of the array.

2fill in blank

medium

Complete the code to use the forEach method to print each fruit.

Javascript

const fruits = ['apple', 'banana', 'cherry'];
fruits.forEach([1] => {
  console.log([1]);
});

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

Aitem

Bfruit

Cfruits

Dindex

Attempts:

3 left

💡 Hint

Common Mistakes

Using the plural array name as the parameter.

Using index when the element itself is needed.

The forEach method takes a function with one parameter representing each element. Here, fruit is that parameter.

3fill in blank

hard

Fix the error in the code to correctly print each element doubled.

Javascript

const nums = [1, 2, 3];
for (const [1] of nums) {
  console.log([1] * 2);
}

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

Anum

Bnums

Cindex

Di

Attempts:

3 left

💡 Hint

Common Mistakes

Using the array name instead of the element variable.

Using an index variable in a for...of loop.

Using num as the variable name for each element in the array is correct. nums is the array itself.

4fill in blank

hard

Fill both blanks to create an object mapping each word to its length for words longer than 3 letters.

Javascript

const words = ['cat', 'elephant', 'dog', 'horse'];
const lengths = {};
for (const [1] of words) {
  if ([2].length > 3) {
    lengths[[2]] = [2].length;
  }
};

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

Aword

Bwords

Attempts:

3 left

💡 Hint

Common Mistakes

Using the array name instead of the element variable.

Using different variable names in the two blanks.

We use word as the variable for each element. The object maps each word to its length.

5fill in blank

hard

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

Javascript

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

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

An

C**

D*

Attempts:

3 left

💡 Hint

Common Mistakes

Using different variable names in filter and map.

Using * instead of ** for exponentiation.

We use n as the variable for each number. The filter keeps even numbers, and map squares them using the exponent operator **.