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58 interview questions on Javascript - Fundamentalsfor developers (2026)

Test your technical skills before an interview of Javascript - Fundamentals with 58 corrected questions. Beginner, Intermediate or Expert level.

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58 questions
Medium
118 votes4501 runs
6 comments

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

Web developer
Vincent Cotroat Jan 18, 2024
Medium
49 votes4132 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 votes4224 runs
2 comments

Fix the following Javascript loop:

Web developer
loops
conditions
Anonymous authorat Apr 27, 2023
Easy
13 votes4631 runs
5 comments

The certificate variable is not attainable outside the if loop

Web developer
variables
scope
Anonymous authorat Apr 6, 2022
Easy
13 votes4360 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 votes4665 runs0 comment

What can be said about ECMAScript?

Web developer
standards
javascript
Anonymous authorat Apr 12, 2022
Easy
12 votes4429 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
Medium
11 votes4522 runs
7 comments

Print the number of countries in the array travel.

Web developer
array
for loop
Vincent Cotroat Sep 5, 2022
Easy
11 votes4399 runs2 comments

Write a for in loop in Javascript

Web developer
arrays
loops
Anonymous authorat Apr 6, 2022
Easy
11 votes3361 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 votes4647 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 votes1069 runs0 comment

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

Web developer
Raphaëlat Feb 28, 2025
Easy
8 votes4500 runs
2 comments

Filter the elements of an array in Javascript

Web developer
array
filter
Anonymous authorat Apr 6, 2022
Easy
7 votes4363 runs0 comment

Add Lyon to the end of the city array

Web developer
arrays
push
Anonymous authorat Mar 29, 2022
Medium
7 votes3008 runs
1 comment

Get the current page URL in Javascript

Web developer
javascript
url
Damienat Sep 4, 2023
Medium
7 votes1708 runs3 comments

Access the value of the 'level' attribute in a Javascript object

Web developer
objects
arrays
Anonymous authorat Mar 21, 2022
Easy
6 votes4450 runs
2 comments

What type is the variable 'apple'?

Web developer
boolean
variable
Anonymous authorat Mar 21, 2022
Hard
6 votes3209 runs
3 comments

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
6 votes1828 runs
1 comment

What does the variable "promise" take in attribute(s)?

Web developer
promises
functions
Vincent Cotroat May 16, 2022
Easy
5 votes2411 runs1 comment

Explain the difference between let and const in Javascript

Web developer
variables
mutability
Anonymous authorat Mar 21, 2022