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129 interview questions on Javascriptfor developers (2023)

Test your technical skills before an interview of Javascript with 129 corrected questions. Beginner, Intermediate or Expert level.

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129 questions
Hard
15 votes976 runs2 comments

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

Web developer
Javascript
arrays
functions
Vincent Cotroat Mar 28, 2023
Easy
6 votes1674 runs0 comment

The certificate variable is not attainable outside the if loop

Web developer
Javascript
variables
scope
Kahinaat Apr 6, 2022
Hard
6 votes1564 runs1 comment

Write a Javascript code that prints the indexes of an array.

Front-end developer
Javascript
array
for loop
Jean-marie Cléryat Nov 8, 2023
Hard
4 votes1640 runs0 comment

What will this code display?

Front-end developer
Javascript
function
identity
Jean-marie Cléryat Jan 4, 2022
Medium
4 votes1633 runs0 comment

What can we say about the following code?

Front-end developer
Javascript
variables
Jean-marie Cléryat Jan 4, 2022
Medium
4 votes1630 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
Javascript
arrays
console.log
push
Jean-marie Cléryat Jan 4, 2022
Medium
4 votes902 runs1 comment

Write a JavaScript function that fetches data from an API and logs it to the console.

Web developer
Javascript
promises
async
Vincent Cotroat Mar 28, 2023
Hard
4 votes199 runs1 comment

How to overwrite a property in an object in Javascript

Front-end developer
Javascript
objects
duplicates
Vincent Cotroat Sep 19, 2022
Hard
3 votes1586 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
3 votes1571 runs
1 comment

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

Web developer
Javascript
array
spread operator
Kahinaat Apr 6, 2022
Easy
3 votes1551 runs
2 comments

Write a for in loop in Javascript

Web developer
Javascript
arrays
loops
Kahinaat Apr 6, 2022
Hard
3 votes611 runs2 comments

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

Web developer
Javascript
objects
arrays
Kahinaat Mar 21, 2022
Medium
3 votes243 runs1 comment

Print the value of the variable name and age in the function sayHi()

Front-end developer
Javascript
functions
variables
Vincent Cotroat Sep 19, 2022
Medium
3 votes188 runs0 comment

Compare two numbers in Javascript

Front-end developer
Javascript
equality
comparison
type
Vincent Cotroat Sep 19, 2022
Easy
2 votes1714 runs0 comment

What can be said about ECMAScript?

Web developer
Javascript
standards
Kahinaat Apr 12, 2022
Hard
2 votes1624 runs1 comment

What is the value of `obj.hello` after executing these few lines of code?

Front-end developer
Javascript
objects
arrays
strings
Jean-marie Cléryat Oct 20, 2023
Hard
2 votes1618 runs0 comment

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

Front-end developer
Javascript
prototype
constructor
Jean-marie Cléryat Jan 4, 2022
Hard
2 votes1597 runs1 comment

How to call a function inside a function in Javascript

Front-end developer
Javascript
functions
objects
Jean-marie Cléryat Jan 4, 2022
Hard
2 votes1562 runs0 comment

Invert a string in Javascript

Front-end developer
Javascript
arrays
strings
Jean-marie Cléryat Jan 4, 2022
Hard
2 votes1539 runs0 comment

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

Front-end developer
Javascript
function
prototype
Jean-marie Cléryat Jan 4, 2022
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