135 interview questions on Javascript for developers (2024)

Hard

53 votes2542 runs4 comments

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

Web developer

Vincent Cotroat Jan 18, 2024

Medium

28 votes2339 runs3 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

16 votes2498 runs1 comment

Fix the following Javascript loop:

Web developer

loops

conditions

Camilleat Apr 27, 2023

Easy

9 votes3011 runs1 comment

The certificate variable is not attainable outside the if loop

Web developer

variables

scope

Kahinaat Apr 6, 2022

Easy

8 votes2854 runs2 comments

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

Web developer

array

spread operator

Kahinaat Jul 19, 2024

Hard

8 votes2020 runs1 comment

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

Front-end developer

javascript

equality

Jean-marie Cléryat Jan 4, 2022

Hard

6 votes1987 runs

3 comments

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

Front-end developer

array

for loop

Jean-marie Cléryat Nov 8, 2023

Easy

5 votes3033 runs0 comment

What can be said about ECMAScript?

Web developer

standards

javascript

Kahinaat Apr 12, 2022

Hard

5 votes2822 runs2 comments

Print the number of countries in the array travel.

Web developer

array

for loop

Vincent Cotroat Sep 5, 2022

Hard

5 votes2080 runs0 comment

What will this code display?

Front-end developer

javascript

function

identity

Jean-marie Cléryat Jan 4, 2022

Easy

5 votes2021 runs

1 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

Hard

5 votes2017 runs

1 comment

Invert a string in Javascript

Front-end developer

arrays

strings

Jean-marie Cléryat Jan 4, 2022

Hard

5 votes222 runs1 comment

How to overwrite a property in an object in Javascript

Front-end developer

objects

duplicates

Vincent Cotroat Sep 19, 2022

Easy

4 votes2827 runs2 comments

Write a for in loop in Javascript

Web developer

arrays

loops

Kahinaat Apr 6, 2022

Easy

4 votes2814 runs0 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

Hard

4 votes2046 runs

2 comments

What is the value of `obj.hello` after executing these few lines of code?

Front-end developer

objects

arrays

strings

Jean-marie Cléryat Oct 20, 2023

Easy

4 votes1903 runs1 comment

Explain the difference between let and const in Javascript

Web developer

variables

mutability

Kahinaat Mar 21, 2022

Hard

4 votes1557 runs

1 comment

Write a switch statement in Javascript that checks if a person is allowed to go down a slide.

Web developer

switch

if else conditions

Mathisat Oct 20, 2023

Medium

3 votes2975 runs0 comment

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

Kahinaat Apr 6, 2022

Hard

3 votes2055 runs

1 comment

Explain the difference between `proto` and `prototype` in Javascript

Front-end developer

prototype

constructor

Jean-marie Cléryat Jan 4, 2022

135 interview questions on Javascriptfor developers (2024)

Test your technical skills before an interview of Javascript with 135 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

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

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

What can be said about ECMAScript?

Print the number of countries in the array travel.

What will this code display?

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

Invert a string in Javascript

How to overwrite a property in an object in Javascript

Write a for in loop in Javascript

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

What is the value of `obj.hello` after executing these few lines of code?

Explain the difference between let and const in Javascript

Write a switch statement in Javascript that checks if a person is allowed to go down a slide.

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

Explain the difference between `proto` and `prototype` in Javascript

135 interview questions on Javascriptfor developers (2024)

Test your technical skills before an interview of Javascript with 135 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

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

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

What can be said about ECMAScript?

Print the number of countries in the array travel.

What will this code display?

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

Invert a string in Javascript

How to overwrite a property in an object in Javascript

Write a for in loop in Javascript

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

What is the value of `obj.hello` after executing these few lines of code?

Explain the difference between let and const in Javascript

Write a switch statement in Javascript that checks if a person is allowed to go down a slide.

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

Explain the difference between `__proto__` and `prototype` in Javascript

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

Explain the difference between `proto` and `prototype` in Javascript