Reduce method in Javascript - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to sum all numbers in the array using reduce.

Javascript

const numbers = [1, 2, 3, 4];
const total = numbers.reduce((acc, curr) => acc [1] curr, 0);
console.log(total);

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

A+

B-

C*

D/

Attempts:

3 left

💡 Hint

Common Mistakes

Using subtraction or multiplication instead of addition.

Forgetting to provide the initial value 0.

The reduce method combines all elements by adding them together using the + operator.

2fill in blank

medium

Complete the code to find the product of all numbers using reduce.

Javascript

const nums = [2, 3, 4];
const product = nums.reduce((acc, curr) => acc [1] curr, 1);
console.log(product);

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

A+

B*

C-

D/

Attempts:

3 left

💡 Hint

Common Mistakes

Using addition instead of multiplication.

Not setting the initial value to 1.

To multiply all numbers, use the * operator inside reduce.

3fill in blank

hard

Fix the error in the reduce function to concatenate all strings in the array.

Javascript

const words = ['I', 'love', 'coding'];
const sentence = words.reduce((acc, curr) => acc [1] curr);
console.log(sentence);

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

A/

B-

C*

D+

Attempts:

3 left

💡 Hint

Common Mistakes

Using arithmetic operators other than + for strings.

Not providing an initial value, which can cause errors with empty arrays.

Strings are combined using the + operator to concatenate them.

4fill in blank

hard

Fill both blanks to create an object counting how many times each word appears.

Javascript

const words = ['apple', 'banana', 'apple', 'orange', 'banana', 'apple'];
const count = words.reduce((acc, curr) => {
  acc[curr] = (acc[curr] [1] 0) [2] 1;
  return acc;
}, {});
console.log(count);

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

A||

B+

C-

D*

Attempts:

3 left

💡 Hint

Common Mistakes

Using arithmetic operators instead of logical OR for default value.

Forgetting to add 1 to increment the count.

The expression acc[curr] = (acc[curr] || 0) + 1; means if acc[curr] exists, use it; otherwise, use 0, then add 1.

5fill in blank

hard

Fill all three blanks to create a new object with uppercase keys and values doubled if greater than 10.

Javascript

const data = {a: 5, b: 15, c: 8};
const result = Object.entries(data).reduce((acc, [1]) => {
  const [key, value] = [2];
  if (value [3] 10) {
    acc[key.toUpperCase()] = value * 2;
  }
  return acc;
}, {});
console.log(result);

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

Aentry

C>

Ditem

Attempts:

3 left

💡 Hint

Common Mistakes

Using different variable names inconsistently.

Using wrong comparison operators like < or ==.

We use item as the parameter for the reduce callback and destructure it to get key and value. The condition checks if value > 10.