Frontend Interview (Mock) | Most Asked JavaScript and ReactJS Questions in 2024 🎉

Welcome to our frontend interview mock session! In this tutorial, we will cover some of the most commonly asked questions in frontend interviews, specifically focusing on JavaScript and ReactJS. By practicing these questions, you will be better prepared to ace your next frontend interview.

Before we dive into the questions, let’s briefly discuss the importance of preparing for a frontend interview. Frontend development is a crucial aspect of any web application, as it is responsible for creating the user interface that users interact with. Employers look for candidates with a strong understanding of JavaScript and ReactJS, as these are widely used technologies in frontend development.

Now, let’s move on to the most commonly asked questions in frontend interviews for 2024:

1. What is JavaScript and why is it important in web development?
   JavaScript is a high-level, interpreted programming language that is widely used for creating interactive and dynamic websites. It is an essential technology in web development because it allows developers to add functionality to web pages, such as form validation, animations, and dynamic content updates.

2. What is the difference between let, const, and var in JavaScript?

   • var is function-scoped and can be redeclared and reassigned.
   • let is block-scoped and can be reassigned but not redeclared.
   • const is block-scoped and cannot be redeclared or reassigned.

3. Explain hoisting in JavaScript.
   Hoisting is a JavaScript mechanism where variable and function declarations are moved to the top of their containing scope during the compilation phase. This allows you to use a variable or function before it has been declared.

4. What is a closure in JavaScript?
   A closure is a function that has access to its own scope, the scope of the outer function, and the global scope. Closures are commonly used in JavaScript for data encapsulation and to create private variables and functions.

5. What are ReactJS components and how do you create them?
   ReactJS components are reusable building blocks that encapsulate specific functionality and UI elements. There are two types of components in React: functional components and class components. Functional components are simple functions that return JSX, while class components are ES6 classes that extend React.Component.

6. Explain the Virtual DOM in ReactJS.
   The Virtual DOM is a lightweight copy of the actual DOM that React uses to perform efficient updates to the UI. When changes are made to a React component, React compares the Virtual DOM with the actual DOM, determines the difference, and updates only the necessary parts of the UI. This results in a faster and more efficient rendering process.

7. What are props and state in ReactJS?

   • Props are read-only data that are passed from parent to child components. They are used to customize and configure components.
   • State is mutable data that is managed by a component and can be updated using the setState method. State is used to store component-specific data that can change over time.
8. How do you handle events in ReactJS?
   In ReactJS, you can handle events by using event handlers. Event handlers are functions that are triggered in response to user interactions, such as clicking a button or typing in an input field. You can attach event handlers to elements using JSX syntax, such as onClick for handling click events.

By practicing these questions and understanding the underlying concepts, you will be well-prepared for your next frontend interview. Good luck! 🚀