Top 50 JavaScript Interview Questions And Answers

These 50 JavaScript questions will enforce your knowledge and confidence for your next interview.

White board coding interview
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When trying to get a position in a new company as a JavaScript developer, whether it be Front-end, Back-end, or Mobile Apps, you will very likely need to face a technical interview.

This interview will show to your potential future employer your level of skills in programming with JavaScript, it may require you to do some whiteboard examples or just a simple question and answer type of an interview.

Some people perform well, some don't, because one of the factors is that you apply to a position that is appropriate to you. But in any case, preparation is the key.

By studying and simulating a test will enforce your knowledge and build up your confidence, the more questions you go through, the more likely you will get one of those questions.

I created a list of 50 questions that go from beginner to advanced level, try to answer them first by yourself, and then check the answer. Try to respond to as many of them as you can and take notes on those you don't know or got wrong.

If you think I missed some important questions from the list let me know in the comments.


  1. What is JavaScript? Answer
  2. How to write comments in JavaScript? Answer
  3. Can you list all JavaScript Data Types? Answer
  4. What an object represents in Javascript? Answer
  5. What is a function in Javascript? Answer
  6. Can you write an example of named function in JavaScript? Answer
  7. Can you write an example of an anonymous function? Answer
  8. Explain the difference between "==" and "==="? Answer
  9. What is the difference between var, let, and const? Answer
  10. What is closure in JavaScript? Answer
  11. Can you name 3 loop methods in JavaScript? Answer
  12. Can we defined variables with the same names in different scopes? Answer
  13. Can you invert the order in array? Answer
  14. How to empty an array in JavaScript? Answer
  15. What is DOM? Answer
  16. Can you name 2 JavaScript paradimgs? Answer
  17. What is functional programming? Answer
  18. What are the pros and cons of functional programming vs object-oriented programming? Answer
  19. What is object oriented programming? Answer
  20. How can we create an object in JavaScript? Answer
  21. What is a constructor in Javascript? Answer
  22. Explain 'This' operator in JavaScript? Answer
  23. What is function binding? Answer
  24. Can you explain what is an arrow function? Answer
  25. What is the purpost of spread operator? Answer
  26. What is the use of Push method in JavaScript? Answer
  27. What is unshift method in JavaScript? Answer
  28. What is the difference between null & undefined? Answer
  29. What is asynchronous programming? Answer
  30. What is Promise in Javascript? Answer
  31. What are callbacks? Answer
  32. What is memoization? Answer
  33. Can you explain WeakSet in javascript. Answer
  34. Can you explain WeakMap in javascript. Answer
  35. What is an event bubbling in JavaScript? Answer
  36. What is a prototype in Javascript? Answer
  37. What is the function of delete operator? Answer
  38. How do you check if an object is an array or not? Answer
  39. What is a pure function in Javascript? Answer
  40. What is an async function? Answer
  41. What is await operator? Answer
  42. What is hoisting in Javascript? Answer
  43. How can we handle exceptions? Answer
  44. What is the difference between classical inheritance and prototypal inheritance? Answer
  45. What is Currying in javascript? Anwser
  46. Can you write an example of an arrow function returning an object literal? Answer
  47. What is a Temporal Dead Zone? Answer
  48. What is the difference between Call and Apply? Answer
  49. How to clone an object in JavaScript? Answer
  50. What optional chaining operator does? Answer


Bojan Vidanovic

Bojan Vidanovic is a computer programmer and tech geek. Love making internet products, blogging, learning, reading, calisthenics and fitness enthusiast.

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