10 ReactJS Interview Questions:

1. What is JSX?
   JSX is a syntax extension for JavaScript that allows developers to write components using a combination of HTML and JavaScript. It is used in ReactJS to define the structure and content of a component.
2. What is the Virtual DOM?
   The Virtual DOM is a lightweight in-memory representation of the actual DOM (Document Object Model). ReactJS uses the Virtual DOM to improve the performance of web applications by only updating the necessary components when a change occurs.
3. What is the purpose of a component in ReactJS?
   A component in ReactJS is a reusable piece of code that represents a part of a web page. Components can be thought of as small, independent building blocks that make up a larger application.
4. What is the difference between a state and a prop in ReactJS?
   A state is a way of storing data within a component that can change over time, whereas a prop is a way of passing data from a parent component to a child component.
5. What are lifecycle methods in ReactJS?
   Lifecycle methods are methods that get called at specific points during the lifecycle of a component. These methods include componentDidMount, componentDidUpdate, and component will unmount.
6. What is the difference between a controlled and uncontrolled component in ReactJS?
   A controlled component is a component that has its state controlled by the parent component, while an uncontrolled component has its own internal state.
7. What is the purpose of a Higher Order Component (HOC) in ReactJS?
   A Higher Order Component (HOC) is a way of reusing component logic. It is a function that takes in a component and returns a new component with additional functionality.
8. What is the difference between a stateless and stateful component in ReactJS?
   A stateless component is a component that does not have its own state, whereas a stateful component has its own state.
9. What is the difference between a functional and class component in ReactJS?
   A functional component is a component that is defined as a function, whereas a class component is a component that is defined as a class.
10. How does ReactJS handle events?
    ReactJS handles events using synthetic events, which are a cross-browser wrapper around the browser’s native event system. This allows ReactJS to handle events in a consistent manner across different browsers.