139 interview questions on Javascript for developers (2026)

Medium

118 votes4550 runs

6 comments

Understanding the differences between `map()` and `forEach()` methods in JavaScript

Web developer

Vincent Cotroat Jan 18, 2024

Medium

50 votes4175 runs4 comments

Write a JavaScript function that fetches data from an API and logs it to the console.

Web developer

promises

async

Vincent Cotroat Mar 28, 2023

Easy

32 votes4264 runs

2 comments

Fix the following Javascript loop:

Web developer

loops

conditions

Anonymous authorat Apr 27, 2023

Easy

14 votes4668 runs

5 comments

The certificate variable is not attainable outside the if loop

Web developer

variables

scope

Anonymous authorat Apr 6, 2022

Easy

13 votes4464 runs

3 comments

Use spread operator to split an array into two arrays in Javascript

Web developer

array

spread operator

Anonymous authorat Jul 19, 2024

Easy

13 votes4395 runs

1 comment

Write a Javascript code that displays 'Adversity is not to be feared' and 'There is potentially a real danger'

Web developer

booleans

conditionals

Adrienat Mar 30, 2022

Easy

12 votes4698 runs0 comment

What can be said about ECMAScript?

Web developer

standards

javascript

Anonymous authorat Apr 12, 2022

Medium

11 votes4557 runs

7 comments

Print the number of countries in the array travel.

Web developer

array

for loop

Vincent Cotroat Sep 5, 2022

Easy

11 votes4436 runs2 comments

Write a for in loop in Javascript

Web developer

arrays

loops

Anonymous authorat Apr 6, 2022

Easy

11 votes3396 runs

1 comment

Find the index of the last element of an array in JavaScript

Web developer

arrays

index

Axelat Sep 4, 2023

Medium

10 votes4689 runs

3 comments

Write a switch statement that checks if a person can go down a slide based on their weight and height.

Web developer

switch

if else conditions

Anonymous authorat Apr 6, 2022

Hard

10 votes2438 runs3 comments

Write a Javascript code that prints the indexes of an array.

Front-end developer

array

for loop

Jean-marie Cléryat Nov 8, 2023

Hard

10 votes1114 runs0 comment

How to filter unique values from an array in Javascript?

Web developer

Raphaëlat Feb 28, 2025

Hard

9 votes2472 runs

2 comments

Which of the following equality(s) are true? 0 == '', 'f' + 1 == 'f1'

Front-end developer

javascript

equality

Jean-marie Cléryat Jan 4, 2022

Easy

9 votes2458 runs0 comment

Which of the following is the most optimized method for creating a literal object?

Front-end developer

javascript

objects

Jean-marie Cléryat Jan 4, 2022

Easy

8 votes4541 runs

2 comments

Filter the elements of an array in Javascript

Web developer

array

filter

Anonymous authorat Apr 6, 2022

Hard

8 votes2538 runs0 comment

What will this code display?

Front-end developer

javascript

function

identity

Jean-marie Cléryat Jan 4, 2022

Easy

7 votes4396 runs0 comment

Add Lyon to the end of the city array

Web developer

arrays

push

Anonymous authorat Mar 29, 2022

Medium

7 votes3034 runs

2 comments

Get the current page URL in Javascript

Web developer

javascript

url

Damienat Sep 4, 2023

Hard

7 votes2522 runs0 comment

Identify the reasons why this code will not work correctly:

Front-end developer

javascript

html

form

Jean-marie Cléryat Jan 4, 2022

139 interview questions on Javascriptfor developers (2026)

Test your technical skills before an interview of Javascript with 139 corrected questions. Beginner, Intermediate or Expert level.

Understanding the differences between `map()` and `forEach()` methods in JavaScript

Write a JavaScript function that fetches data from an API and logs it to the console.

Fix the following Javascript loop:

The certificate variable is not attainable outside the if loop

Use spread operator to split an array into two arrays in Javascript

Write a Javascript code that displays 'Adversity is not to be feared' and 'There is potentially a real danger'

What can be said about ECMAScript?

Print the number of countries in the array travel.

Write a for in loop in Javascript

Find the index of the last element of an array in JavaScript

Write a switch statement that checks if a person can go down a slide based on their weight and height.

Write a Javascript code that prints the indexes of an array.

How to filter unique values from an array in Javascript?

Which of the following equality(s) are true? 0 == '', 'f' + 1 == 'f1'

Which of the following is the most optimized method for creating a literal object?

Filter the elements of an array in Javascript

What will this code display?

Add Lyon to the end of the city array

Get the current page URL in Javascript

Identify the reasons why this code will not work correctly:

139 interview questions on Javascriptfor developers (2026)

Test your technical skills before an interview of Javascript with 139 corrected questions. Beginner, Intermediate or Expert level.

Understanding the differences between `map()` and `forEach()` methods in JavaScript

Write a JavaScript function that fetches data from an API and logs it to the console.

Fix the following Javascript loop:

The certificate variable is not attainable outside the if loop

Use spread operator to split an array into two arrays in Javascript

Write a Javascript code that displays 'Adversity is not to be feared' and 'There is potentially a real danger'

What can be said about ECMAScript?

Print the number of countries in the array travel.

Write a for in loop in Javascript

Find the index of the last element of an array in JavaScript

Write a switch statement that checks if a person can go down a slide based on their weight and height.

Write a Javascript code that prints the indexes of an array.

How to filter unique values ​​from an array in Javascript?

Which of the following equality(s) are true? 0 == '', 'f' + 1 == 'f1'

Which of the following is the **most optimized** method for creating a literal object?

Filter the elements of an array in Javascript

What will this code display?

Add Lyon to the end of the city array

Get the current page URL in Javascript

Identify the reasons why this code will not work correctly:

How to filter unique values from an array in Javascript?

Which of the following is the most optimized method for creating a literal object?