After javascript can be executed on the server side, it has become very popular. So for better understanding and quality code, there are few concepts that a developer must know. So here are javascript interview questions generally asked in the interviews

1) What is event bubbling and capturing?

2) Best practices in javascript?

3) How to reduce the loading time of web page without concerning too much refactoring?

4) If two div on the page has the same id(“mydiv”) then getelementbyid(“mydiv”) will refer to ?

5) How to handle large JSON on UI if rendering is slow?

6) The result of accessing undeclared variable?

7) Parent/Child communication in javascript ?

8) How to make Ajax call?

9) What is setTimeout?

10) What are closures?

11) What is a prototype in javascript?

12) Scope in javascript?

13) How to define the class in javascript?

14) How can promises be implemented in javascript?

15) # and ! in URL?

16) What are callbacks?

17) Suppose we have an error in production which is not producible on Local and we don’t have access to the production and we have only minified file the production then how you can track the error?

18) What is async and defer?

19) How to find the inner classes of a div by using javascript?

20) What is the difference between promise and callback?

21) What is view engine?

22) What are bind filters and reduce map in js?

23) Difference between primitive and non-primitives data types?

24) How javascript interpret DOM that is rendering order or control flow?

25) What is the hoisting?

26) Difference between following two snippets 

function abc(){
  return “Sunil”
var abc = function(){
   return “Sunil”;
27) Inheritance in javascript?
28) Local scope and block level scope in javascript?

29) What is lexical scope?


Further Reading