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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 votes2272 runs3 comments
Hard
8 votes2307 runs
2 comments
Hard
7 votes2379 runs0 comment

What will this code display?

Front-end developer
javascript
function
identity
Jean-marie Cléryat Jan 4, 2022
Hard
7 votes2329 runs
1 comment

Invert a string in Javascript

Front-end developer
arrays
strings
Jean-marie Cléryat Jan 4, 2022
Easy
7 votes2301 runs0 comment
Hard
5 votes2351 runs0 comment
Medium
5 votes2285 runs0 comment
Hard
5 votes2278 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 votes248 runs1 comment
Hard
4 votes2429 runs1 comment
Hard
4 votes2334 runs1 comment
Hard
4 votes2321 runs
2 comments
Hard
4 votes2307 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 votes2386 runs
1 comment
Hard
3 votes2365 runs1 comment
Hard
3 votes2353 runs
1 comment
Hard
3 votes2348 runs3 comments

Write a function that returns a string 'Haha!'

Front-end developer
functions
return
Jean-marie Cléryat Jan 4, 2022
Hard
3 votes2330 runs
1 comment
Hard
3 votes2289 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