Introduction

As a budding developer or someone learning programming, it's crucial to familiarize yourself with popular frameworks and libraries. ReactJS is one such popular JavaScript library used for building user interfaces. As you progress in your programming journey, you'll likely encounter ReactJS technical questions during coding interviews.

In this blog post, we will explore the top 20 ReactJS technical interview questions and provide you with detailed answers, code examples, and analogies to help you understand the concepts better. So, let's get started!

1. What is ReactJS, and what are its key features?

Interview Question: Explain ReactJS and its key features.

Answer: ReactJS, often referred to as React, is an open-source JavaScript library developed by Facebook for building user interfaces, specifically for single-page applications. It enables developers to create reusable UI components, manage the state of the app, and efficiently update the UI as the state changes.

Key features of ReactJS include:

• Virtual DOM: React creates a lightweight in-memory data structure called the Virtual DOM, which is an abstract representation of the actual DOM. This feature allows React to efficiently update the UI by calculating the difference between the current and new Virtual DOM (called "diffing") and then updating the real DOM with only the necessary changes.
• Component-based architecture: React follows a component-based architecture, where complex UIs can be broken down into smaller, reusable components. Each component has its own logic, state, and can render itself independently.
• One-way data binding: React follows a unidirectional data flow, meaning the data is passed down from parent components to child components through properties (props). This approach makes it easier to trace and debug the flow of data in an application.
• JSX: JSX (JavaScript XML) is a syntax extension for JavaScript that allows you to write HTML-like structures within JavaScript code. It makes the code more readable and easier to understand.

Here's a simple example of a React component using JSX:

import React from 'react';

function Hello(props) {
  return <h1>Hello, {props.name}!</h1>;
}

export default Hello;

2. What is the difference between functional and class components?

Interview Question: Differentiate between functional and class components in React.

Answer: In React, components can be defined using either functions or classes. The main differences between functional and class components are as follows:

• Functional components (also known as stateless or dumb components) are plain JavaScript functions that accept props as an argument and return a React element. They are primarily used for presenting data and don't have access to the component's state or lifecycle methods. However, with the introduction of React Hooks, functional components can now manage state and access lifecycle methods.

Example of a functional component:

import React from 'react';

function Greeting(props) {
  return <h1>Hello, {props.name}!</h1>;
}

export default Greeting;

• Class components (also known as stateful or smart components) are JavaScript ES6 classes that extend the React.Component class. They have access to component state and lifecycle methods, making them suitable for managing data and complex UI logic.

Example of a class component:

import React, { Component } from 'react';

class Greeting extends Component {
  render() {
    return <h1>Hello, {this.props.name}!</h1>;
  }
}

export default Greeting;

With the introduction of React Hooks, functional components have become more powerful, and the use of class components has declined. However, it's still essential to understand both types of components for coding interviews and legacy codebases.

3. What are React props?

Interview Question: Explain the concept of React props and their usage.

Answer: Props (short for "properties") are a way to pass data from parent components to child components in React. Props are read-only, meaning that child components should not modify the data passed to them through props.

Props are passed as attributes to child components and can be accessed within the child component using the props object. Here's an example of how to pass and use props in React:

Parent component:

import React from 'react';
import ChildComponent from './ChildComponent';

function ParentComponent() {
  const message = 'Hello from ParentComponent';

  return <ChildComponent text={message} />;
}

export default ParentComponent;

Child component:

import React from 'react';

function ChildComponent(props) {
  return <h1>{props.text}</h1>;
}

export default ChildComponent;

In this example, the ParentComponent passes the message variable as a prop named text to the ChildComponent. The ChildComponent then accesses the text prop using props.text and renders it in an <h1> element.

4. What is state in React, and how is it managed?

Interview Question: Describe the concept of state in React and how it is managed.

Answer: In React, the state refers to an object that holds the data or information required to render a component. The state is mutable and can change over time, causing the component to re-render whenever there's a change in the state.

In class components, the state is managed using the this.state object and the this.setState() method. The this.state object holds the initial state of the component, while the this.setState() method is used to update the state.

Here's an example of managing state in a class component:

import React, { Component } from 'react';

class Counter extends Component {
  constructor(props) {
    super(props);
    this.state = {
      count: 0,
    };
  }

  incrementCounter = () => {
    this.setState({ count: this.state.count + 1 });
  };

  render() {
    return (
      <div>
        <h1>Count: {this.state.count}</h1>
        <button onClick={this.incrementCounter}>Increment</button>
      </div>
    );
  }
}

export default Counter;

In functional components, the state can be managed using the useState hook. The useState hook is a function that takes the initial state as an argument and returns an array containing the current state and a function to update the state.

Here's an example of managing state in a functional component using the useState hook:

import React, { useState } from 'react';

function Counter() {
  const [count, setCount] = useState(0);

  const incrementCounter = () => {
    setCount(count + 1);
  };

  return (
    <div>
      <h1>Count: {count}</h1>
      <button onClick={incrementCounter}>Increment</button>
    </div>
  );
}

export default Counter;

5. What are React lifecycle methods?

Interview Question: Explain the concept of lifecycle methods in React.

Answer: Lifecycle methods are special methods in class components that allow you to execute code at specific points during the component's lifecycle. The lifecycle of a React component can be divided into three main phases:

1. Mounting: This phase occurs when a component is being created and inserted into the DOM. The following lifecycle methods are called during this phase:
2. constructor(): Called when the component is being created. It's used to initialize the state and bind event handlers.
3. static getDerivedStateFromProps(): Called before the component is rendered. It's used to update the state based on changes in the props.
4. render(): Called to generate the JSX representation of the component. It's the only required lifecycle method.

componentDidMount(): Called after the component is inserted into the DOM. It's used for fetching data, setting up subscriptions, or other side effects.

Updating: This phase occurs when a component's state or props change, causing the component to re-render. The following lifecycle methods are called during this phase:

1. static getDerivedStateFromProps(): Called before the component is re-rendered. It's used to update the state based on changes in the props.
2. shouldComponentUpdate(): Called before the component is re-rendered. It's used to determine if the component should re-render based on changes in the state or props.
3. render(): Called to generate the JSX representation of the component.
4. getSnapshotBeforeUpdate(): Called before the DOM is updated. It's used to capture information from the DOM (e.g., scroll position) before the update.

componentDidUpdate(): Called after the component is re-rendered and the DOM is updated. It's used to perform side effects, like updating the data or subscriptions.

Unmounting: This phase occurs when a component is being removed from the DOM. The following lifecycle method is called during this phase:

1. componentWillUnmount(): Called before the component is removed from the DOM. It's used to clean up resources, like timers or subscriptions, to prevent memory leaks.

With the introduction of React Hooks, lifecycle methods can now be replicated using hooks like useEffect in functional components, minimizing the need for class components.

6. What are React Hooks, and what are the most commonly used hooks?

Interview Question: Explain the concept of React Hooks and the most commonly used hooks.

Answer: React Hooks are functions introduced in React 16.8 that allow you to use state and other React features in functional components instead of class components. Hooks enable you to reuse stateful logic between components without changing the component hierarchy.

The most commonly used hooks are:

1. useState: This hook allows you to add state to functional components. It takes the initial state as an argument and returns an array containing the current state and a function to update the state.

Example of using useState:

import React, { useState } from 'react';

function Counter() {
  const [count, setCount] = useState(0);

  const incrementCounter = () => {
    setCount(count + 1);
  };

  return (
    <div>
      <h1>Count: {count}</h1>
      <button onClick={incrementCounter}>Increment</button>
    </div>
  );
}

export default Counter;

1. useEffect: This hook allows you to perform side effects, like fetching data or updating the DOM, in functional components. It takes two arguments: a function containing the side effect and an optional dependency array. The side effect function is called whenever the dependencies change or the component mounts/unmounts.

Example of using useEffect:

import React, { useState, useEffect } from 'react';

function DataFetcher() {
  const [data, setData] = useState([]);

  useEffect(() => {
    fetch('https://api.example.com/data')
      .then((response) => response.json())
      .then((data) => setData(data));
  }, []); // Empty dependency array ensures the effect runs only once

  return (
    <div>
      {data.map((item) => (
        <p key={item.id}>{item.name}</p>
      ))}
    </div>
  );
}

export default DataFetcher;

1. useContext: This hook allows you to access the value of a React context without using the Context.Consumer component. It takes the context object as an argument and returns the current context value.

Example of using useContext:

import React, { useContext } from 'react';
import { ThemeContext } from './ThemeContext';

function ThemedButton() {
  const theme = useContext(ThemeContext);

  return <button style={{ background: theme.background, color: theme.foreground }}>Themed Button</button>;
}

export default ThemedButton;

There are other built-in hooks like useReducer, useCallback, useMemo, and useRef. Developers can also create custom hooks to share stateful logic between components.

7. What is the virtual DOM, and how does it work?

The virtual DOM (vDOM) is an in-memory representation of the actual DOM (Document Object Model). In React, whenever there is an update or change in the component's state, a new virtual DOM is created instead of updating the real DOM directly. The virtual DOM is much faster than the real DOM because updating the real DOM directly can be expensive in terms of performance.

React uses a technique called "diffing" to compare the new virtual DOM with the old one. It identifies the differences (or "diffs") between the two and then updates only the parts of the real DOM that have changed. This process is known as "reconciliation" and helps to optimize the performance of React applications.

Here's an analogy to help you understand the concept of virtual DOM:

Think of the real DOM as a large, complicated jigsaw puzzle. Each time you make a change, you need to take the whole puzzle apart and put it back together again. On the other hand, the virtual DOM is like having a second, identical puzzle that you can quickly update. You can then compare the two puzzles and only change the pieces that are different. This way, you avoid the time-consuming process of rebuilding the entire puzzle from scratch.

8. What is JSX, and why is it used in React?

JSX (JavaScript XML) is a syntax extension for JavaScript that allows you to write HTML-like code within your JavaScript code. It's not a programming language, but rather a way to describe the structure and appearance of your UI (User Interface) components using a familiar syntax.

React uses JSX to define the structure and appearance of components. It makes the code more readable and easier to understand, especially when dealing with complex UIs. JSX is not required to use React, but it's highly recommended and widely adopted in the community.

Here's an example of a simple React component using JSX:

function Welcome(props) {
  return <h1>Hello, {props.name}</h1>;
}

Without JSX, the same component would look like this:

function Welcome(props) {
  return React.createElement('h1', null, `Hello, ${props.name}`);
}

As you can see, the JSX version is more readable and easier to understand.

9. How do you handle events in React?

In React, event handling is similar to handling events in plain HTML, but with some differences in syntax. For example, instead of using the onclick attribute in HTML, you would use the onClick attribute in React. Additionally, event handlers in React are written in camelCase, and you pass a function as the event handler instead of a string.

Here's an example of handling a button click event in React:

import React from 'react';

function ButtonClick() {
  const handleClick = () => {
    alert('Button clicked!');
  };

  return <button onClick={handleClick}>Click me</button>;
}

export default ButtonClick;

In this example, we define a handleClick function that will be called when the button is clicked. We then pass this function as the event handler to the onClick attribute of the button.

When using class components, you need to be careful with the value of this inside event handlers. To ensure that this refers to the component instance, you can either bind the event handler in the constructor or use an arrow function.

Here's an example of handling a button click event in a class component:

import React, { Component } from 'react';

class ButtonClick extends Component {
  handleClick() {
    alert('Button clicked!');
  }

  render() {
    return <button onClick={this.handleClick.bind(this)}>Click me</button>;
  }
}

export default ButtonClick;

Or using an arrow function:

import React, { Component } from 'react';

class ButtonClick extends Component {
  handleClick = () => {
    alert('Button clicked!');
  };

  render() {
    return <button onClick={this.handleClick}>Click me</button>;
  }
}

export default ButtonClick;

10. What are controlled and uncontrolled components?

In React, form elements like input, textarea, and select can be handled as either controlled or uncontrolled components.

Controlled Components

Controlled components are form elements whose values are controlled by the React state. In a controlled component, the form element's value is directly linked to the component's state, and any change in the form element's value will update the state.

Here's an example of a controlled input component:

import React, { useState } from 'react';

function ControlledInput() {
  const [inputValue, setInputValue] = useState('');

  const handleChange = (event) => {
    setInputValue(event.target.value);
  };

  return (
    <div>
      <input type="text" value={inputValue} onChange={handleChange} />
      <p>Entered value: {inputValue}</p>
    </div>
  );
}

export default ControlledInput;

In this example, the input element's value is set using the value attribute and is linked to the inputValue state. When the input value changes, the handleChange function is called, which updates the state with the new value.

Uncontrolled Components

Uncontrolled components are form elements whose values are managed by the DOM itself, not by the React state. To access the values of uncontrolled components, you use a ref to get direct access to the DOM element.

Here's an example of an uncontrolled input component:

import React, { useRef } from 'react';

function UncontrolledInput() {
  const inputRef = useRef();

  const handleClick = () => {
    alert(`Entered value: ${inputRef.current.value}`);
  };

  return (
    <div>
      <input type="text" ref={inputRef} />
      <button onClick={handleClick}>Show entered value</button>
    </div>
  );
}

export default UncontrolledInput;

In this example, we use a ref to access the input element directly. When the button is clicked, the handleClick function is called, which retrieves and displays the input value using the ref.

In general, it's recommended to use controlled components because they make it easier to manage form data and validate user input.

11. What is the context API?

The Context API is a feature in React that allows you to share data between components without having to pass it through props. This can be helpful when you need to pass data through multiple levels of a component tree, or when you have a global state that should be accessible by multiple components.

To create a context, you can use the React.createContext function:

const MyContext = React.createContext();

This will create a context object with two components, MyContext.Provider and MyContext.Consumer.

MyContext.Provider is a component that wraps the part of the component tree that needs access to the shared data. It has a value prop that takes the data you want to share.

Here's an example of using the context provider:

import React from 'react';
import MyComponent from './MyComponent';
import MyContext from './MyContext';

function App() {
  const sharedData = { text: 'Hello from context!' };

  return (
    <MyContext.Provider value={sharedData}>
      <MyComponent />
    </MyContext.Provider>
  );
}

export default App;

MyContext.Consumer is a component that can be used inside the component tree to access the shared data. It takes a function as a child, which receives the context value as an argument.

Here's an example of using the context consumer:

import React from 'react';
import MyContext from './MyContext';

function MyComponent() {
  return (
    <MyContext.Consumer>
      {(context) => <p>{context.text}</p>}
    </MyContext.Consumer>
  );
}

export default MyComponent;

In this example, the MyComponent component uses the MyContext.Consumer component to access the shared data from the context.

You can also use the useContext hook to access the context value in functional components:

import React, { useContext } from 'react';
import MyContext from './MyContext';

function MyComponent() {
  const context = useContext(MyContext);
  return <p>{context.text}</p>;
}

export default MyComponent;

The Context API is a convenient way to share state and data between components, but it's not a replacement for state management libraries like Redux, which provide more features and optimizations for managing complex state.

12. What are Higher-Order Components (HOCs)?

Higher-Order Components (HOCs) are a pattern in React for reusing component logic. HOCs are functions that take a component as an argument and return a new component with additional props or behavior.

Here's an example of a simple HOC that logs the props of the wrapped component:

function withLogging(WrappedComponent) {
  return function LoggingComponent(props) {
    console.log('Props:', props);
    return <WrappedComponent {...props} />;
  };
}

In this example, the withLogging function takes a WrappedComponent as an argument and returns a new LoggingComponent that logs the props and renders the WrappedComponent with the same props.

To use the HOC, you can wrap your component like this:

import React from 'react';
import withLogging from './withLogging';

function MyComponent(props) {
  return <p>Hello, {props.name}!</p>;
}

export default withLogging(MyComponent);

This will create a new component that includes the logging behavior, and you can use it just like the original component.

HOCs can be used to inject additional props, modify existing props, or add new behavior to components. They can also be composed together to create more complex components.

Keep in mind that HOCs can introduce some issues, like naming collisions or extra component layers in the React tree. Many of these issues can be mitigated by using React Hooks, which provide a more flexible and composable way to reuse logic between components.

13. What is React Router, and how do you use it?

React Router is a popular third-party library for managing navigation and rendering components based on the browser URL in React applications. It provides a declarative way to define routes and navigate between components.

To use React Router, you need to install the react-router-dom package:

npm install react-router-dom

Then, you can import the necessary components from the package and use them in your application.

Here's a basic example of using React Router:

import React from 'react';
import { BrowserRouter as Router, Route, Link, Switch } from 'react-router-dom';
import HomeComponent from './HomeComponent';
import AboutComponent from './AboutComponent';
import NotFoundComponent from './NotFoundComponent';

function App() {
  return (
    <Router>
      <nav>
        <ul>
          <li>
            <Link to="/">Home</Link>
          </li>
          <li>
            <Link to="/about">About</Link>
          </li>
        </ul>
      </nav>
      <Switch>
        <Route exact path="/" component={HomeComponent} />
        <Route path="/about" component={AboutComponent} />
        <Route component={NotFoundComponent} />
      </Switch>
    </Router>
  );
}

export default App;

In this example, we wrap our application in a Router component, which manages the browser history and provides the necessary context for the other routing components.

We use the Link component to create navigation links, which update the browser URL when clicked.

The Switch component is used to render the first matching Route component based on the current URL. If no matching route is found, it renders the NotFoundComponent.

React Router provides many other features, like route parameters, nested routes, and navigation hooks. You can learn more about these features in the official documentation.

14. What are keys in React, and why are they important?

Keys are a special attribute in React used to help identify and track elements in a list. When rendering a list of elements, each element should have a unique key prop to help React determine which elements have changed, been added, or been removed when updating the DOM.

Here's an example of using keys when rendering a list of items:

import React from 'react';

function ItemList({ items }) {
  return (
    <ul>
      {items.map((item) => (
        <li key={item.id}>{item.text}</li>
      ))}
    </ul>
  );
}

export default ItemList;

In this example, we assign a unique key prop to each li element based on the item.id property.

Keys should be unique among siblings, and they should not be based on the index of the element in the list, as this can cause issues with the update and reordering process. Instead, use a unique identifier from your data, like an ID or a combination of properties that make the element unique.

Using keys correctly can improve the performance of your application and help prevent bugs related to component updates and state management.

15. What is useCallback, and when should you use it?

useCallback is a hook in React that allows you to memoize a function, so it doesn't get recreated on every render of the component. This can be useful when you want to optimize the performance of your application by preventing unnecessary re-renders of child components that depend on the memoized function.

The useCallback hook takes two arguments: the function you want to memoize and an array of dependencies. The hook returns a memoized version of the function, which will only be recreated if any of the dependencies change.

Here's an example of using useCallback:

import React, { useCallback, useState } from 'react';

function ExpensiveComponent({ onClick }) {
  console.log('ExpensiveComponent rendered');
  return <button onClick={onClick}>Click me</button>;
}

function App() {
  const [count, setCount] = useState(0);

  const handleClick = useCallback(() => {
    setCount((prevCount) => prevCount + 1);
  }, []);

  return (
    <div>
      <ExpensiveComponent onClick={handleClick} />
      <p>Count: {count}</p>
    </div>
  );
}

export default App;

In this example, we use useCallback to memoize the handleClick function, which updates the count state. The ExpensiveComponent takes this memoized function as a prop and renders a button that calls it when clicked.

Since the handleClick function doesn't change between renders, the ExpensiveComponent will not re-render when the count state changes, which can improve the performance of the application.

Keep in mind that useCallback should be used sparingly and only when necessary, as it can introduce additional complexity and overhead to your code. In many cases, using a regular function or an inline arrow function is sufficient and more efficient.

16. What is useMemo, and when should you use it?

useMemo is a hook in React that allows you to memoize the result of a function so that it doesn't get recomputed on every render of the component. This can be useful when you want to optimize the performance of your application by preventing unnecessary calculations or data transformations.

The useMemo hook takes two arguments: a function that computes the memoized value and an array of dependencies. The hook returns the memoized value, which will only be recomputed if any of the dependencies change.

Here's an example of using useMemo:

import React, { useMemo, useState } from 'react';

function App() {
  const [count, setCount] = useState(0);

  const expensiveComputation = (value) => {
    console.log('Expensive computation');
    return value * 10;
  };

  const memoizedResult = useMemo(() => expensiveComputation(count), [count]);

  const handleClick = () => {
    setCount((prevCount) => prevCount + 1);
  };

  return (
    <div>
      <button onClick={handleClick}>Increase count</button>
      <p>Count: {count}</p>
      <p>Memoized result: {memoizedResult}</p>
    </div>
  );
}

export default App;

In this example, we use useMemo to memoize the result of the expensiveComputation function, which takes the count state as an argument. Since the memoized result is only recomputed when the count state changes, the expensiveComputation function is not called on every render, which can improve the performance of the application.

Keep in mind that useMemo should be used sparingly and only when necessary, as it can introduce additional complexity and overhead to your code. In many cases, computing the value directly or using a regular function is sufficient and more efficient.

17. What is React.Children, and when should you use it?

React.Children is a utility provided by React to help you work with the children prop in a more consistent and flexible way. It provides methods for counting, mapping, or iterating over the children, as well as other utility functions.

Here's an example of using React.Children.map to wrap each child in a div element:

import React from 'react';

function WrapperComponent({ children }) {
  return (
    <div>
      {React.Children.map(children, (child) => (
        <div className="wrapper">{child}</div>
      ))}
    </div>
  );
}

export default WrapperComponent;

In this example, the WrapperComponent takes a children prop and uses React.Children.map to render each child inside a div element with a wrapper class.

You can use React.Children when you need more control over the rendering or processing of the children in a component, or when you want to ensure that your components work correctly with different types of children, like arrays, strings, or elements.

18. What is the difference between React.PureComponent and React.Component?

React.PureComponent is a subclass of React.Component that implements a shallow comparison for checking if the component should update. This means that PureComponent only re-renders when its props or state have changed in a shallow manner, which can lead to performance improvements in some cases.

Here's a comparison between a regular component and a pure component:

import React from 'react';

class RegularComponent extends React.Component {
  render() {
    console.log('RegularComponent rendered');
    return <div>{this.props.value}</div>;
  }
}

class PureComponentExample extends React.PureComponent {
  render() {
    console.log('PureComponentExample rendered');
    return <div>{this.props.value}</div>;
  }
}

export { RegularComponent, PureComponentExample };

In this example, we have two components, RegularComponent and PureComponentExample. The PureComponentExample extends React.PureComponent instead of React.Component. If we pass the same props to both components and update the parent component, RegularComponent will re-render regardless of whether its props have changed, while PureComponentExample will only re-render if its props have changed, which can lead to better performance.

However, it's important to note that PureComponent only performs a shallow comparison of props and state. This means that if you're passing complex data structures like nested objects or arrays, it may not update correctly, and you might need to implement a custom shouldComponentUpdate method in your component.

19. What is PropTypes, and how do you use it?

PropTypes is a library used to define the types of props that a component should receive, helping you to catch errors during development. It is not included in the React core library, but it's widely used in the React community.

To use PropTypes, you need to install it as a dependency:

npm install prop-types

Then, you can import it into your component and define the types of your props:

import React from 'react';
import PropTypes from 'prop-types';

function Welcome({ name, age }) {
  return (
    <div>
      <h1>Hello, {name}!</h1>
      <p>You are {age} years old.</p>
    </div>
  );
}

Welcome.propTypes = {
  name: PropTypes.string.isRequired,
  age: PropTypes.number.isRequired,
};

export default Welcome;

In this example, we're defining the propTypes of the Welcome component. The name prop should be a string and is required, while the age prop should be a number and is also required. If the component receives props of the wrong type or if a required prop is not provided, a warning will be displayed in the console during development.

Keep in mind that PropTypes is only for development purposes, and it does not validate props in production builds.

20. What is the difference between React.createRef and useRef?

React.createRef and useRef are two ways to create a reference to a DOM element or an instance of a class component in React.

React.createRef is used in class components, while useRef is a hook that can be used in functional components. Here's an example of using each method to create a reference to an input element:

import React, { useRef } from 'react';

class ClassComponentExample extends React.Component {
  constructor(props) {
    super(props);
    this.inputRef = React.createRef();
  }

  componentDidMount() {
    this.inputRef.current.focus();
  }

  render() {
    return <input ref={this.inputRef} />;
  }
}

function FunctionalComponentExample() {
  const inputRef = useRef();

  React.useEffect(() => {
    inputRef.current.focus();
  }, []);

  return <input ref={inputRef} />;
}

export { ClassComponentExample, FunctionalComponentExample };

In the ClassComponentExample, we use React.createRef in the constructor to create a reference and assign it to this.inputRef. In the FunctionalComponentExample, we use the useRef hook to create a reference and store it in the inputRef variable.

Both methods allow you to access the DOM element or component instance through the current property of the reference. In this example, we're focusing the input element when the component mounts.

In general, if you're using functional components with hooks, you should use useRef to create references. If you're still using class components, you can use React.createRef.

Conclusion

In this blog post, we've covered 20 common ReactJS technical questions that you might encounter in coding interviews. We've provided explanations and code examples to help you understand the concepts and prepare for your interview.

Remember that practice makes perfect, and the more you work with React and its ecosystem, the more comfortable you'll become with these concepts. Good luck with your coding interviews, and happy coding!