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Express.js

58 Express.js interview questions

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Express.js Fundamentals


  • 1.

    What is Express.js, and how does it relate to Node.js?

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  • 2.

    Explain the concept of middleware in Express.js.

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  • 3.

    How would you set up a basic Express.js application?

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  • 4.

    What is the purpose of the app.use() function?

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  • 5.

    How do you serve static files using Express.js?

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  • 6.

    Discuss the difference between app.get() and app.post() in Express.js.

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  • 7.

    How do you retrieve the URL parameters from a GET request in Express.js?

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  • 8.

    What are route handlers, and how would you implement them?

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  • 9.

    How do you enable CORS in an Express.js application?

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  • 10.

    Explain the use of next() in Express.js middleware.

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Routing and Requests


  • 11.

    What is the role of the express.Router class?

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  • 12.

    How do you handle 404 errors in Express.js?

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  • 13.

    What are the differences between req.query and req.params?

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  • 14.

    Describe the purpose of req.body and how you would access it.

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  • 15.

    How do you create a middleware that logs the request method and URL for every request?

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  • 16.

    Explain how you would implement nested routes in Express.js.

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  • 17.

    How can you capture and respond to URL parameters in a route?

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  • 18.

    How do you serve different content types (e.g., JSON, HTML) with Express.js responses?

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  • 19.

    What are best practices for structuring a large Express.js application with multiple routes?

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Middleware and Error Handling


  • 20.

    Explain the concept and use of built-in middleware in Express.js.

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  • 21.

    How do you write custom middleware functions in Express.js?

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  • 22.

    How do you handle file uploads in Express.js?

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  • 23.

    What is express-session, and how would you use it?

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  • 24.

    Discuss error handling in an Express.js application. How do you define an error-handling middleware?

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  • 25.

    Provide an example of using third-party middleware, such as body-parser or morgan.

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  • 26.

    How do you protect against SQL injection or other security threats in Express.js?

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Response and Performance


  • 27.

    How would you implement caching in an Express.js application?

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  • 28.

    How do you set cookies and get cookies in an Express.js application?

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  • 29.

    What are ways to improve the performance of Express.js applications?

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  • 30.

    How do you configure an Express.js app for a reverse proxy, like Nginx?

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  • 31.

    Explain the purpose of template engines. How would you integrate one with Express.js?

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Testing and Debugging


  • 32.

    How do you test an Express.js application?

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  • 33.

    Discuss common debugging techniques for Express.js applications.

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  • 34.

    What is the role of environment variables in an Express.js application?

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  • 35.

    How do you use a debugger with an Express.js app running in Node.js?

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Express.js with Databases


  • 36.

    How would you connect a MongoDB database with an Express.js application?

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  • 37.

    Explain how to integrate an ORM like Sequelize with Express.js.

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  • 38.

    How do you handle database errors in Express.js?

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  • 39.

    What are the advantages of using a database pooling mechanism in an Express.js app?

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Authentication and Authorization


  • 40.

    Describe how you would implement user authentication in Express.js.

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  • 41.

    Explain how sessions are managed in Express.js.

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  • 42.

    Discuss how you would handle user roles and permissions in an Express.js application.

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  • 43.

    How can you secure passwords and sensitive information in your Express.js app?

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Integration and Configuration


  • 44.

    How do you integrate a third-party API in an Express.js application?

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  • 45.

    Explain the steps to deploy an Express.js application to a cloud provider like AWS or Heroku.

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  • 46.

    How can you ensure that your Express.js application is scalable_?

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  • 47.

    What is the Twelve-Factor App methodology, and how does it apply to Express.js?

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Coding Challenges


  • 48.

    Write an Express.js middleware function that limits requests to 100 per hour per IP address.

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  • 49.

    Create an Express.js route that accepts a JSON payload and responds with the same payload in reverse order.

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  • 50.

    Develop a simple REST API with Express.js that includes CRUD operations for managing books. Include route definitions and handler functions that interact with a placeholder data store.

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Advanced Topics and Best Practices


  • 51.

    Discuss strategies for building a real-time application with Express.js.

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  • 52.

    What are some common optimization techniques for Express.js applications?

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  • 53.

    Explain the concept and benefits of server-side rendering with Express.js and a templating engine.

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  • 54.

    How do you ensure that your Express.js code is maintainable and follows best practices?

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Case Studies and Scenario-Based Questions


  • 55.

    How would you structure an Express.js application for a large-scale e-commerce platform?

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  • 56.

    Describe the key considerations for building a secure API with Express.js.

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  • 57.

    Discuss how to handle session management in a distributed Express.js application.

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  • 58.

    What are the implications of microservices architecture for an Express.js application?

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