Top 80+ JavaScript Interview Questions and Answers for 2024 [Updated]

JavaScript is one of the most popular programming languages in the world, and it plays a crucial role in web development. As a JavaScript developer, you can expect to encounter a wide range of questions during a job interview. To help you prepare, we have compiled a list of the top 80+ JavaScript interview questions and answers for 2024. Whether you are a beginner or an experienced developer, these questions will help you brush up on your knowledge and feel confident during your next interview.

General JavaScript Interview Questions

1. What is JavaScript?

JavaScript is a high-level, interpreted programming language used to create dynamic, interactive, and customizable web pages. It is also commonly used in both front-end and back-end web development.

2. What are the key features of JavaScript?

JavaScript is known for its features such as being lightweight, interpreted, easy to learn, object-oriented, and having a rich set of libraries.

3. What is the use of console.log in JavaScript?

The console.log method is used in JavaScript to output data to the console. It is commonly used for debugging and logging information during development.

4. Explain the difference between `let`, `var`, and `const` in JavaScript.

let and const were introduced in ES6 (ECMAScript 2015) and are used for variable declarations. var is the older way of declaring variables in JavaScript.

var has function scope, while let and const have block scope.
Variables declared with let can be reassigned, while variables declared with const cannot be reassigned.

5. What is a closure in JavaScript?

A closure is a function that has access to its own scope, the scope of the function it was defined within, and the global scope. These functions â€œrememberâ€ the environment in which they were created.

JavaScript Data Types and Operators

6. What are the primitive data types in JavaScript?

The primitive data types in JavaScript are string, number, boolean, null, undefined, and symbol (added in ES6).

7. What is the use of the `===` operator in JavaScript?

The === operator in JavaScript is used for strict equality comparison. It compares both the value and the type of the operands.

8. What is the `typeof` operator in JavaScript?

The typeof operator in JavaScript is used to determine the data type of its operand. It returns a string that represents the data type.

9. Explain truthy and falsy values in JavaScript.

In JavaScript, a value is considered truthy if it converts to true when evaluated in a Boolean context. Conversely, a value is considered falsy if it converts to false.

10. How are arrays and objects different in JavaScript?

Arrays are an ordered collection of values, while objects are a collection of key-value pairs. Arrays use numerical indexes, while objects use keys to access values.

JavaScript Functions and Scope

11. What is a callback function in JavaScript?

A callback function in JavaScript is a function that is passed as an argument to another function and is invoked after a certain task is completed.

12. Explain the concept of hoisting in JavaScript.

Hoisting in JavaScript refers to the process in which variable and function declarations are moved to the top of their containing scope during compilation.

13. What is an IIFE (Immediately Invoked Function Expression)?

An IIFE is a JavaScript function that is executed immediately after it is defined. It is a common pattern used to create local scopes and avoid polluting the global namespace.

14. What is the difference between `apply` and `call` in JavaScript?

Both apply and call are methods in JavaScript used to call a function with a specific this value and arguments provided. The difference lies in how the additiona...

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