Most Asked JavaScript Interview Questions

Preparing for a JavaScript interview can be daunting, given the vastness of the language and its applications. To help you get ready, I have compiled a comprehensive list of the most commonly asked JavaScript interview questions, grouped by topic. Whether you are a beginner or an advanced developer, these questions cover essential concepts, advanced topics, and OOPS Concepts. Use this guide to enhance your understanding and boost your confidence for your upcoming interviews.

Basic JavaScript Concepts

1. What is JavaScript? How is it different from Java?

2. What are the data types in JavaScript?

3. Explain the difference betweennullandundefined?

4. How do you declare a variable in JavaScript?

5. What are the differences betweenvar,let, andconstin terms of variable scope and hoisting?

6. What is the scope?

7. What are the global scope, local scope, and block scope?

8. What is the difference between function declarations and function expressions?

9. What are arrow functions? How do they differ from regular functions?

Advanced JavaScript Concepts

1. What is a higher-order function?

2. Explain the map(), filter(), reduce(), some(), and every() array methods?

3. Custom map(), filter(), and reduce() array methods?

4. What is the JavaScript Runtime environment?

5. Explain the concept of hoisting.

6. what is the Execution context in JS?

7. What is concurrency in JavaScript and why is it single-threaded?

8. What is a closure? Provide an example.

9. What is the event loop in JavaScript?

10. What is the difference between synchronous and asynchronous programming?

11. Explain the concept of callbacks and how they are used to handle asynchronous operations.

12. What are promises in JavaScript? How do you handle promise chaining?

13. Explainasync/awaitand how it simplifies asynchronous programming.

14. What is the difference between a shallow copy and a deep copy of an object?

15. What is the use of thethiskeyword in JavaScript?

16. Explain Call(),apply(), andbind()?

OOPS Concept

1. What is a constructor function?

2. What are prototypes in JavaScript? How are they related to inheritance?

3. What are classes in JavaScript?

4. Explain inheritance in JavaScript.

5. Explain encapsulation in JavaScript.

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