Advanced JavaScript Interview Questions

Last updated on Feb 07, 2024
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Advanced JavaScript Interview Questions

Over the years, JavaScript has become one of the most influential programming languages in the software industry. Due to this, there are a number of job applications and applicants in this industry. Due to this, we decided to come up with the actual Advanced JavaScript Interview Questions, questions that actually matter while you create codes for your company. Have a read on these questions to cement your knowledge in JavaScript and get that dream job. But, over time, we have found out that many developers lack a basic understanding of JavaScript such as working on objects and working on obsolete patterns like deeply layered inheritance hierarchies.

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We have created this section for your convenience from where you can navigate to all the sections of the article. All you need to just click or tap on the desired topic or the section, and it will land you there.

JavaScript Coding Interview Questions

Here in this article, we will be listing frequently asked Advanced JavaScript Interview Questions and Answers with the belief that they will be helpful for you to gain higher marks. Also, to let you know that this article has been written under the guidance of industry professionals and covered all the current competencies.

Q11. What is closure in JavaScript with a real time example?

A function that can access its parent scope, even after the parent function has closed is called JavaScript closure.

const parentMethod = () => {
  const title = 'Advanced JavaScript Questions';
  const innerMethod = () => {

In other words, a closure gives you access to an outer function's scope from an inner function.

Q12. How do you find the min and max element of the array?

const items = [40, 10, 11, 15, 25, 21, 5];


Find max value

console.log(Math.max(...items)); // 40

Find min value

console.log(Math.min(...items)); // 5

Q13. What will be the output of the following code?

let x = null;



Q14. How to display a table of any number in JavaScript?

const displayTable = (number) => {
    const numbers = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]; 
    const countingArray = => {

Q15. Why prototype is used in JavaScript?

JavaScript is a dynamic language and at any time we can add new properties to an object and can be shared among all the instances. Hence to add new properties and implement inheritance prototypes are used.


function Candidate() { = 'Arun';
    this.role = 'QA';
var candidateObj1 = new Candidate();
candidateObj1.salary = 10000;
console.log(candidateObj1.salary); // 10000
var candidateObj2 = new Candidate();
console.log(candidateObj2.salary); // undefined

Prototype in JavaScript
A prototype is an internal object that is associated with the functions automatically it is available, modified, or add additional variables or methods for it, and then share across all functions of their constructor.
Q16. What are the new data types in ES6 JavaScript?
The following are the different types of data types used in JavaScript.
  • Numbers: Can represent both floating-point and integer numbers. Example: 5, 6.5, 7 etc.
  • String: A sequence of characters is called a string. Strings can be enclosed in JavaScript within single or double quotes. Example: "Advanced JavaScript Questions" etc.
  • Boolean: This represents a logical entity. It can have either true or false values.
  • Null: This type only has one value: null
  • Undefined: A variable whose value has yet to be assigned is undefined.
  • Symbol: It is not a primitive data type that can be used to represent literal forms. It is a built-in object whose constructor returns a unique symbol.
  • bigint: This is the bigint type that represents whole numbers larger than 253-1. You must add the letter n to the end of the number in order to form a literal bigint number.
  • Object: This is the most crucial data-type. It forms the foundation for modern JavaScript. These data types will be discussed in more detail in future articles.

Note: We have a list of all interview questions related to ES6. These are really helpful in cracking your interviews.

Q17. What is the output of following code?

const displayText = () => {
    setTimeout(() => {
    }, 0)



Q18. What is the output of the res given scenario?

const res = [];
res.x = 5;
res.x = 10;


[ x: 10 ]

Q19. What will be the output of the below given code?

const list = [1, 2, 3, 4, 5, 6];
const list2 = [5, 6, 7, 8, 9, 10];
console.log([...list, ...list2]);


[ 1, 2, 3, 4, 5, 6, 5, 6, 7, 8, 9, 10 ]

Q20. What will be the output of the result in given code?

const list = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10];
const result = list.find((item) => {
    return item > 3;



Top 10 Advanced JavaScript Interview Questions

Here you will find the list of Top Advanced JavaScript Interview Questions, which were written under the supervision of industry experts. These are the most common questions and usually asked in every interview for the role of the JavaScript Developers.

  • What is prototype?
  • What is Callback hell?
  • What is callback?
  • What are the difference between arrow functions & normal functions?
  • What is JavaScript Hoisting?
  • What are the difference between let, var & const?
  • What is Promises?
  • What is the difference between Map & filter function?
  • How to remove duplicate values in array?
  • What are Closure?
  • What is rest & spread operators?
  • What are the data types used in JavaScript?
Reviewed and verified by Umesh Singh
Umesh Singh

My name is Umesh Singh having 11+ experience in Node.JS, React JS, Angular JS, Next JS, PHP, Laravel, WordPress, MySQL, Oracle, JavaScript, HTML and CSS etc. I have worked on around 30+ projects. I lo...