JavaScript Interview Questions and Answers

Are you preparing for a JavaScript interview? Do you want to know what kind of questions you might face during the interview? If yes, then you have come to the right place. In this article, we will discuss some of the most common JavaScript interview questions and their answers.

JavaScript is one of the most popular programming languages in the world. It is used to create dynamic and interactive web pages. Many companies are looking for skilled JavaScript developers who can create complex web applications. If you are one of those developers, then you should be prepared for the interview.

Basic JavaScript Interview Questions

Let's start with some basic JavaScript interview questions.

Q1. What is JavaScript?

JavaScript is a high-level, interpreted programming language that is used to create dynamic and interactive web pages. It is a client-side scripting language that runs on the user's web browser.

Q2. What are the data types in JavaScript?

JavaScript has six primitive data types: string, number, boolean, null, undefined, and symbol. It also has one non-primitive data type, which is object.

Q3. What is the difference between null and undefined?

Null is a value that represents the intentional absence of any object value. Undefined is a value that represents an uninitialized variable or an object property that does not exist.

Q4. What is the difference between == and === operators?

The == operator compares the values of two operands, while the === operator compares both the values and the data types of two operands.

Q5. What is hoisting in JavaScript?

Hoisting is a JavaScript mechanism where variables and function declarations are moved to the top of their respective scopes before the code is executed.

Intermediate JavaScript Interview Questions

Now, let's move on to some intermediate JavaScript interview questions.

Q6. What is closure in JavaScript?

A closure is a function that has access to its outer function's variables, even after the outer function has returned.

Q7. What is the difference between let and var?

The let keyword declares a block-scoped variable, while the var keyword declares a function-scoped variable.

Q8. What is the difference between const and let?

The const keyword declares a block-scoped variable that cannot be reassigned, while the let keyword declares a block-scoped variable that can be reassigned.

Q9. What is the difference between synchronous and asynchronous code?

Synchronous code is executed in a sequential order, while asynchronous code is executed in a non-sequential order.

Q10. What is the event loop in JavaScript?

The event loop is a mechanism in JavaScript that allows asynchronous code to be executed in a non-blocking way.

Advanced JavaScript Interview Questions

Finally, let's move on to some advanced JavaScript interview questions.

Q11. What is prototypal inheritance in JavaScript?

Prototypal inheritance is a mechanism in JavaScript where objects inherit properties and methods from their prototype object.

Q12. What is the difference between call and apply methods?

The call method is used to call a function with a given this value and arguments provided individually, while the apply method is used to call a function with a given this value and arguments provided as an array.

Q13. What is the difference between bind and call methods?

The bind method is used to create a new function with a given this value and arguments provided individually, while the call method is used to call a function with a given this value and arguments provided individually.

Q14. What is the difference between a promise and a callback?

A promise is an object that represents the eventual completion or failure of an asynchronous operation, while a callback is a function that is passed as an argument to another function and is executed when the other function has completed its task.

Q15. What is the difference between a closure and a module?

A closure is a function that has access to its outer function's variables, while a module is a self-contained piece of code that encapsulates related functionality.

Conclusion

JavaScript is a powerful and versatile programming language that is used to create dynamic and interactive web pages. If you are preparing for a JavaScript interview, then you should be familiar with the basic, intermediate, and advanced JavaScript interview questions. We hope that this article has helped you to understand some of the most common JavaScript interview questions and their answers. Good luck with your interview!

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