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80 interview questions on Javascriptfor developers (2025)

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

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80 questions
Hard
10 votes2290 runs3 comments
Hard
8 votes2327 runs
2 comments
Hard
7 votes2402 runs0 comment

What will this code display?

Front-end developer
javascript
function
identity
Jean-marie Cléryat Jan 4, 2022
Hard
7 votes2347 runs
1 comment

Invert a string in Javascript

Front-end developer
arrays
strings
Jean-marie Cléryat Jan 4, 2022
Easy
7 votes2319 runs0 comment
Hard
5 votes2371 runs0 comment
Medium
5 votes2306 runs0 comment
Hard
5 votes2296 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
5 votes250 runs1 comment
Hard
4 votes2451 runs1 comment
Hard
4 votes2358 runs1 comment
Hard
4 votes2342 runs
2 comments
Hard
4 votes2332 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
3 votes2408 runs
1 comment
Hard
3 votes2386 runs1 comment
Hard
3 votes2371 runs
1 comment
Hard
3 votes2371 runs3 comments

Write a function that returns a string 'Haha!'

Front-end developer
functions
return
Jean-marie Cléryat Jan 4, 2022
Hard
3 votes2355 runs
1 comment
Hard
3 votes2313 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