Job offersCompaniesTestsBlogI'm an employerSign upLog in
fr
fr
Home>IT Tests>Questions>Javascript

80 interview questions on Javascriptfor developers (2026)

Test your technical skills before an interview of Javascript with 80 corrected questions. Beginner, Intermediate or Expert level.

or
Technology
Profession
Test
Sort by
Newest
Most popular
Last review
Filter by
Published
3952
To review
72
80 questions
Easy
10 votes2500 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
10 votes2479 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
9 votes2512 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
Hard
8 votes2581 runs0 comment

What will this code display?

Front-end developer
javascript
function
identity
Jean-marie Cléryat Jan 4, 2022
Hard
7 votes2562 runs0 comment

Identify the reasons why this code will not work correctly:

Front-end developer
javascript
html
form
Jean-marie Cléryat Jan 4, 2022
Hard
7 votes2537 runs
1 comment

Invert a string in Javascript

Front-end developer
arrays
strings
Jean-marie Cléryat Jan 4, 2022
Easy
6 votes2561 runs2 comments

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
Medium
6 votes2477 runs0 comment

Write a Javascript code that will display the letters A, B, C, D in the console.

Front-end developer
array
function
Jean-marie Cléryat Jan 4, 2022
Hard
6 votes2468 runs0 comment

What will be the first thing that the following code displays?

Front-end developer
inheritance
prototype
constructor
Jean-marie Cléryat Jan 4, 2022
Hard
6 votes269 runs1 comment

How to overwrite a property in an object in Javascript

Front-end developer
objects
duplicates
Anonymous authorat Sep 19, 2022
Hard
5 votes2577 runs1 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
Hard
5 votes2537 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
Hard
5 votes2522 runs0 comment

Explain the 2 phases of event propagation in the DOM.

Front-end developer
event
event propagation
Jean-marie Cléryat Jan 4, 2022
Hard
5 votes2506 runs
2 comments

Which of the following code will log the message 'baz'?

Front-end developer
javascript
function
prototype
Jean-marie Cléryat Jan 4, 2022
Hard
4 votes2625 runs1 comment

Which of the following objects does not exist in modern JavaScript?

Front-end developer
objects
javascript
Jean-marie Cléryat Jan 4, 2022
Hard
4 votes2593 runs
2 comments

Which of the following features are part of version ES2015(formerly ES6)?

Front-end developer
es6
promises
arrow functions
Jean-marie Cléryat Jan 4, 2022
Hard
4 votes2543 runs
2 comments

How to call a function inside a function in Javascript

Front-end developer
functions
objects
Jean-marie Cléryat Jan 4, 2022
Hard
3 votes2560 runs
1 comment

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

Front-end developer
prototype
constructor
Jean-marie Cléryat Jan 4, 2022
Hard
3 votes2552 runs3 comments

Write a function that returns a string 'Haha!'

Front-end developer
functions
return
Jean-marie Cléryat Jan 4, 2022
Hard
3 votes2547 runs0 comment

Which of the following equality(s) returns`true`?

Front-end developer
javascript
NaN
Jean-marie Cléryat Jan 4, 2022
Javascript tests