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Table of contents
1.
Introduction
2.
Most Asked Express JS Interview Questions and Answers
2.1.
1. What is Express.js, and why do you use it?
2.2.
2. How does Express.js handle routing?
2.3.
3. How does Express.js handle middleware?
2.4.
4. How does Express.js handle request and response objects?
2.5.
5. What is the difference between Express.js and Node.js?
2.6.
6. What is the difference between a traditional server and an Express.js server?
2.7.
7. How does Express.js handle error handling?
2.8.
8. What is a template engine, and how does Express.js use it?
2.9.
9. How does Express.js handle file uploads?
2.10.
10. Mention some of the databases with which Express JS is integrated.
2.11.
11. How does Express.js differ from other Node.js frameworks?
2.12.
12. How do you handle errors in Express.js?
2.13.
13. What are middleware functions in Express.js?
2.14.
14. What is a callback function in Express.js?
2.15.
15. What is the difference between res.send() and res.json() in Express.js?
2.16.
16. What is the use of app.use() in Express.js?
2.17.
17. What is the purpose of the next() function in Express.js?
2.18.
18. What is the difference between app.route() and app.use() in Express.js?
2.19.
19. What is the purpose of the req.params object in Express.js?
2.20.
20. What is the difference between req.query and req.params in Express.js?
2.21.
21. What is the purpose of the app.locals object in Express.js?
3.
Frequently Asked Questions
3.1.
What is an express JS interview?
3.2.
Why is express JS better?
3.3.
What is ExpressJS used for?
4.
Conclusion
Last Updated: May 24, 2024

Express.js Interview Questions and Answers

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Introduction

This article will discuss a list of the most asked Express.js interview questions and answers. These questions can help you prepare for your following Express Js interview. Check out the complete list of questions below.

ExpressJS Interview Questions

Most Asked Express JS Interview Questions and Answers

1. What is Express.js, and why do you use it?

Express.js is a web application framework for Node.js. It is an open-source platform for building server-side applications in JavaScript. It provides excellent features and tools to developers to develop web applications efficiently. Express.js helps developers to create and manage their applications and offers a wide range of customization options. 

2. How does Express.js handle routing?

Express.js has a simple routing system that allows developers to define and manage application routes. Routes can be determined using the app.get() and app.post() methods. It can be associated with callback functions executed when a request is made to the route.

3. How does Express.js handle middleware?

Express.js has a middleware system that allows developers to define and manage middleware functions. These functions can perform tasks such as authentication, validation, or modification of request and response objects. Middleware functions are executed in the order they are defined. They can be added to the application using the app.use() method.

4. How does Express.js handle request and response objects?

Express.js has a request and response object system that provides access to information about incoming requests and outgoing responses. The request object contains information about the incoming request, such as the URL, method, and headers. The response object is used to send a response back to the client. Developers can use methods such as res.send(), res.json(), and res.render() to send responses to the client.

5. What is the difference between Express.js and Node.js?

FeatureExpress.jsNode.js
TypeFrameworkRuntime environment
LanguageJavaScriptJavaScript
PurposeTo build web applicationsTo run JavaScript code outside of a browser
FeaturesRouting, middleware, template engines, etc.Event-driven, non-blocking I/O, etc.
DependenciesNode.jsN/A
PopularityVery popularVery popular
ExamplesGitHub, Uber, NetflixPayPal, LinkedIn, Walmart

6. What is the difference between a traditional server and an Express.js server?

A traditional server is a standalone server that is built and managed independently. While an Express.js server is built using the Express.js framework. It runs on top of Node.js. Express.js provides a simple and efficient way to create and manage web applications. It offers a wide range of features and tools for handling routing, middleware, and request or response objects.

7. How does Express.js handle error handling?

Express.js provides an error-handling system that allows developers to define and manage error-handling middleware functions. These functions can be used to catch and handle errors that make in the application. It can be added to the application using the app.use() method.

8. What is a template engine, and how does Express.js use it?

A template engine is a tool used to generate HTML or other output based on dynamic data. Express.js supports several template engines, such as EJS and Handlebars. These engines can dynamically render HTML pages based on data stored in the application.

9. How does Express.js handle file uploads?

Express.js provides support for file uploads through middleware functions and the request object. Developers can use middleware functions like multer or busboy to handle file uploads. It can access the uploaded files through the request object.

10. Mention some of the databases with which Express JS is integrated.

Below are some of the databases that Express JS supports:

  • MySQL
  • MongoDB
  • PostgreSQL
  • SQLite
  • Oracle

11. How does Express.js differ from other Node.js frameworks?

Express.js is a flexible framework that provides only the essential features required for web application development. On the other hand, other Node.js frameworks, such as Meteor, Sails.js, and Koa.js, offer more features but may not be required for smaller projects. Express.js is a good choice for simple, fast, and scalable web applications.

12. How do you handle errors in Express.js?

Express.js provides a built-in error-handling mechanism using the next() function. When an error occurs, you can pass it to the next middleware or route handler using the next() function. You can also add an error-handling middleware to your application that will be executed whenever an error occurs.

13. What are middleware functions in Express.js?

Middleware functions are those functions that can access and modify the request and response objects in an Express application. They can add functionality to an application, such as logging, authentication, and error handling.

14. What is a callback function in Express.js?

A callback function in Express.js is a type of function that is called after a specific action has occurred. For example, a callback function handles a successful or failed database query.

15. What is the difference between res.send() and res.json() in Express.js?

res.send() is used to send a response with any type of data (string, object, buffer, etc.). While res.json() is used to send a JSON response. res.json() also sets the Content-Type header to application or JSON.

16. What is the use of app.use() in Express.js?

app.use() is used to add middleware functions to an Express application. It can be used to add global middleware functions or to add middleware functions to specific routes.

17. What is the purpose of the next() function in Express.js?

The next() function is used to pass control from one middleware function to the next function. It is used to execute the next middleware function in the chain.

18. What is the difference between app.route() and app.use() in Express.js?

app.route() defines multiple route handlers for a single route. While the app.use() function is used to add middleware functions to an application.

19. What is the purpose of the req.params object in Express.js?

The req.params object is used to access route parameters in Express.js. Route parameters capture values from the URL and pass them to the request handler.

20. What is the difference between req.query and req.params in Express.js?

req.query is used to access the query parameters in a URL. While req.params is used to access route parameters in a URL.

21. What is the purpose of the app.locals object in Express.js?

The app.locals object stores application-level data in an Express.js application. This data is available to all templates and routes.

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Frequently Asked Questions

What is an express JS interview?

An Express.js interview is an interview for a job that involves using Express.js. During the interview, the interviewer will likely ask about your experience with Express.js and web development.

Why is express JS better?

Express Js is better because it is lightweight and fast, has a Flexible routing system, supports a large number of middleware modules, has strong community and support, and has easy integration with other technologies.

What is ExpressJS used for?

Express.js is a server-side JavaScript framework used for building web applications. For Example, RESTful APIs, server-side web applications, handling HTTP requests, and integrating with databases.

Conclusion

In conclusion, preparing for an Express.js interview can be hard. With the proper knowledge and practice, you can prepare easily. Express Js interview questions and answers in this article will help you prepare. 

Recommended Readings:

You can also consider our Interview Preparation Course to give your career an edge over others.

 

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