Top 50 JavaScript Interview Questions And Answers

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.

Questions

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