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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.

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135 questions
Medium
32 votes1819 runs3 comments

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

Web developer
Vincent Cotroat Jan 18, 2024
Medium
19 votes1666 runs2 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
11 votes1856 runs1 comment

Fix the following Javascript loop:

Web developer
loops
conditions
Camilleat Apr 27, 2023
Easy
8 votes2390 runs1 comment

The certificate variable is not attainable outside the if loop

Web developer
variables
scope
Kahinaat Apr 6, 2022
Hard
7 votes1797 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
Easy
6 votes2245 runs1 comment

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

Web developer
array
spread operator
Kahinaat Apr 6, 2022
Medium
6 votes1828 runs0 comment

What can we say about the following code?

Front-end developer
javascript
variables
Jean-marie Cléryat Jan 4, 2022
Hard
6 votes1769 runs2 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
5 votes210 runs1 comment

How to overwrite a property in an object in Javascript

Front-end developer
objects
duplicates
Vincent Cotroat Sep 19, 2022
Easy
4 votes2422 runs0 comment

What can be said about ECMAScript?

Web developer
standards
javascript
Kahinaat Apr 12, 2022
Easy
4 votes2235 runs2 comments

Write a for in loop in Javascript

Web developer
arrays
loops
Kahinaat Apr 6, 2022
Easy
4 votes2231 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
Medium
4 votes2165 runs1 comment

Print the number of countries in the array travel.

Web developer
array
for loop
Vincent Cotroat Sep 5, 2022
Hard
4 votes1869 runs0 comment

What will this code display?

Front-end developer
javascript
function
identity
Jean-marie Cléryat Jan 4, 2022
Medium
4 votes1848 runs1 comment

Write a Javascript code that displays the contents of the table : Peter, Paul, Jacques, and the length of the table.

Front-end developer
arrays
console.log
push
Jean-marie Cléryat Jan 4, 2022
Easy
4 votes1830 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
Hard
4 votes1784 runs0 comment

Invert a string in Javascript

Front-end developer
arrays
strings
Jean-marie Cléryat Jan 4, 2022
Easy
4 votes1686 runs1 comment

Explain the difference between let and const in Javascript

Web developer
variables
mutability
Kahinaat Mar 21, 2022
Hard
3 votes1842 runs1 comment

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
Medium
3 votes1835 runs0 comment

How to make an AJAX call to an external domain that makes public data available.

Front-end developer
ajax
authentication
Jean-marie Cléryat Jan 4, 2022
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