How do I prepare for a JavaScript interview?

Work through realistic questions, read why each answer is right, then redo the ones you missed. This test has ten, taken from what interviewers commonly ask a beginner or a junior. Then read the postings: the 1,913 open jobs that name JavaScript show what employers expect on top of it.

Is this JavaScript test free?

Yes. It needs no account and no email, runs in your browser and sends nothing anywhere.

What does my score mean?

It is a self-check. Eight or more right means the basics are fresh; five to seven means a good base with gaps; under five means more practice first. It is not an official certificate.

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JavaScript test: 10 questions to check yourself

In plain words: JavaScript is the programming language of web pages: it makes buttons, menus and forms react to what you do. Answer ten questions, press the button, and see which you got right and why.

1,913 open jobs name JavaScript today, with a median advertised pay of $198K. The questions are the kind that come up in a first interview.

1What is the difference between const and let?const cannot be assigned a new value after it is set, let canconst is fasterlet works only in functionsThere is none

2What does typeof null return?"null""object""undefined""number"

3What is the difference between == and ===?== also converts types before comparing, === does not=== compares only numbersThey are the same== is stricter

4What does [1, 2, 3].map(n => n * 2) return?[2, 4, 6]6[1, 2, 3]undefined

5What is a Promise?A value that is saved in the browserAn object that stands for a result that will arrive later, such as a reply from a serverA way to repeat codeA kind of loop

6What does await do inside an async function?Stops the whole pagePauses that function until the Promise has a resultRuns the code twiceTurns errors off

7What is a closure?A function that remembers the variables around it from where it was createdA way to close the browser windowA function with no nameAn error message

8What does this log? console.log(0.1 + 0.2 === 0.3)truefalseAn errorundefined

9Which method adds an item to the end of an array?pushpopshiftslice

10In a browser, what does document.querySelector(".price") return?Every element with the class priceThe first element with the class priceThe text priceA new element

Questions about this test

How do I prepare for a JavaScript interview?: Work through realistic questions, read why each answer is right, then redo the ones you missed. This test has ten, taken from what interviewers commonly ask a beginner or a junior. Then read the postings: the 1,913 open jobs that name JavaScript show what employers expect on top of it.
Is this JavaScript test free?: Yes. It needs no account and no email, runs in your browser and sends nothing anywhere.
What does my score mean?: It is a self-check. Eight or more right means the basics are fresh; five to seven means a good base with gaps; under five means more practice first. It is not an official certificate.

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