React Router is an essential library for any developer working with React applications. It enables dynamic routing, allowing for seamless navigation and rendering of components based on the URL. This functionality is crucial for creating single-page applications (SPAs) that provide a smooth user experience without the need for full page reloads. React Router’s flexibility and ease of integration make it a go-to solution for managing routes in modern web development.

This article offers a curated selection of interview questions focused on React Router. By familiarizing yourself with these questions and their answers, you’ll be better prepared to demonstrate your expertise in routing and navigation within React applications, showcasing your ability to build efficient and user-friendly web interfaces.

React Router Interview Questions and Answers

1. How do you create a simple route that renders a component when the URL matches /home?

To create a simple route in React Router that renders a component when the URL matches /home, set up the Router and define the Route. React Router is a library for routing in React, enabling navigation among views, changing the browser URL, and keeping the UI in sync with the URL.

Example:

import React from 'react';
import { BrowserRouter as Router, Route, Switch } from 'react-router-dom';

const Home = () => 
Home Component
;

const App = () => (
  
    
      
    
  
);

export default App;

In this example, the Home component is rendered when the URL matches /home. The Router wraps the application, and the Switch groups the Route components. The Route specifies the path and the component to render.

2. Write a route configuration that includes nested routes for a blog application with paths /blog, /blog/:id, and /blog/:id/comments.

Nested routes in React Router allow you to define routes within other routes, creating a hierarchical structure. This is useful for applications with complex navigation, such as a blog with paths like /blog, /blog/:id, and /blog/:id/comments.

Example:

import { BrowserRouter as Router, Route, Switch } from 'react-router-dom';
import Blog from './Blog';
import BlogPost from './BlogPost';
import Comments from './Comments';

function App() {
  return (
    
      
        
        
        
      
    
  );
}

export default App;

In this configuration:

• The /blog path renders the Blog component, displaying a list of blog posts.
• The /blog/:id path renders the BlogPost component, displaying a specific post based on the id parameter.
• The /blog/:id/comments path renders the Comments component, displaying comments for the specific post.

3. How can you pass props to a component rendered by a Route? Provide an example.

In React Router, you can pass props to a component rendered by a Route using the render method instead of the component method. The render method allows you to pass props directly to the component.

Example:

import React from 'react';
import { BrowserRouter as Router, Route } from 'react-router-dom';

const ExampleComponent = ({ message }) => {
  return 
{message}
;
};

const App = () => {
  const message = "Hello, World!";
  
  return (
    
       } 
      />
    
  );
};

export default App;

4. How do you handle 404 errors in a React Router application?

Handling 404 errors in a React Router application involves setting up a catch-all route that matches any path not explicitly defined. This is typically done using a wildcard route that renders a 404 component when no other routes match.

Example:

import { BrowserRouter as Router, Route, Switch } from 'react-router-dom';
import Home from './Home';
import About from './About';
import NotFound from './NotFound';

function App() {
  return (
    
      
        
        
        
      
    
  );
}

export default App;

In this example, the Switch component renders the first route that matches the current location. If none match, the NotFound component is rendered, handling 404 errors.

5. Write a route configuration that uses Redirect to navigate from /old-path to /new-path.

In React Router, the Redirect component is used to navigate from one route to another. This is useful for handling deprecated routes or redirecting users to a new path. The Redirect component can be used within a Route component to specify the old path and the new path.

Example:

import { BrowserRouter as Router, Route, Switch, Redirect } from 'react-router-dom';

function App() {
  return (
    
      
        
          
        
        
          
        
        {/* Other routes */}
      
    
  );
}

function NewPathComponent() {
  return 
Welcome to the new path!
;
}

6. Explain the use of the useParams hook and provide an example of its usage.

The useParams hook in React Router allows you to access the parameters of the current route. This is useful for routes with dynamic segments, such as user IDs or product IDs. By using useParams, you can easily extract these parameters and use them within your component.

Example:

import React from 'react';
import { useParams } from 'react-router-dom';

const UserProfile = () => {
    const { userId } = useParams();

    return (
        

            
User Profile
            
User ID: {userId}
        
    );
};

export default UserProfile;

In this example, the UserProfile component uses the useParams hook to extract the userId parameter from the URL, allowing the component to display the user ID dynamically.

7. How can you programmatically navigate to a different route within a component?

In React Router, programmatic navigation allows you to navigate to different routes within a component without using <Link> or <NavLink>. This is useful for navigation based on certain conditions or events, such as form submissions or button clicks.

For React Router v5, use the useHistory hook:

import { useHistory } from 'react-router-dom';

function MyComponent() {
    const history = useHistory();

    const handleClick = () => {
        history.push('/new-route');
    };

    return (
        Go to New Route
    );
}

For React Router v6, use the useNavigate hook:

import { useNavigate } from 'react-router-dom';

function MyComponent() {
    const navigate = useNavigate();

    const handleClick = () => {
        navigate('/new-route');
    };

    return (
        Go to New Route
    );
}

8. Write a custom hook that logs the current pathname whenever it changes.

In React, custom hooks allow you to extract and reuse stateful logic across multiple components. React Router provides hooks like useLocation to access the current location object, which includes the pathname. By combining these, we can create a custom hook that logs the current pathname whenever it changes.

import { useEffect } from 'react';
import { useLocation } from 'react-router-dom';

function useLogPathname() {
    const location = useLocation();

    useEffect(() => {
        console.log(location.pathname);
    }, [location.pathname]);
}

export default useLogPathname;

9. How would you implement lazy loading of routes in a React application? Provide an example.

Lazy loading in a React application can be achieved using the React.lazy function and Suspense component. This allows you to load components only when they are needed, reducing the initial load time. React Router can be integrated with these features to lazy load routes.

Example:

import React, { Suspense, lazy } from 'react';
import { BrowserRouter as Router, Route, Switch } from 'react-router-dom';

const Home = lazy(() => import('./Home'));
const About = lazy(() => import('./About'));

function App() {
  return (
    
      Loading...