We’re Hiring! Learn More

(480) 641-9611Schedule

Free Estimate

Express.js Interview Questions & Answers Part- 4

Express.js is a lightweight framework built on top of Node.js that helps make web development easier. It simplifies the way we handle server functions and adds useful tools to manage web requests and responses. With Express, you can organize your app better using features like routing and middleware, which help control how your app handles different requests. Express is also a key part of the MEAN stack, which is a popular set of tools used to build full-stack web applications using JavaScript. Developers choose Express because it’s simple to use, flexible, and works well for both small and large projects. One of the biggest advantages of Express is that it helps you create server-side applications quickly and with less effort. Whether you’re building APIs or full web apps, Express offers a smooth setup process and a clear structure, making development faster and more efficient. On this page, we’ve put together important Express.js interview questions and answers for 2025. These questions cover both the basics and more advanced topics in Express.js.

Answer: You can use middleware like express.urlencoded() or express.json() to handle form data and JSON data, respectively, in Express.js. These middleware functions parse the incoming data and make it available in req.body.
Answer: Here are some of the different types of middleware commonly used in Express.js:
  • Application-level middleware
  • Custom middleware
  • Router-level middleware
  • Error-handling middleware
  • Built-in middleware
  • Third-party middleware
Answer: Since Express.js includes a built-in error handling mechanism, I don’t need to write code for this from the beginning. In my previous role, I made sure that errors resulting from asynchronous functions invoked by middleware and route handlers were forwarded to the next() function. This function allows Express.js to detect and handle these errors.
Answer: Express JS offers the following built-in middleware functions:
  • Static: It is used for serving static assets like images, HTML files, etc.
  • JSON: This function is available in Express 4.16.0+ and is used for passing the incoming requests with JSON payloads.
  • URL encoded: This function is also available in Express 4.16.0+ and is used for passing the incoming requests with URL-encoded payloads.
Answer: CORS is the abbreviation for Cross-origin resource sharing. This mechanism is useful to request the restricted resources from another server or domain. This function can be mainly done in the following three ways:
  • Express cors module
  • header() (or res.set()): Multiple headers can be set using this way.
  • setHeader(): Only a single header can be set in this way.
Answer: You can follow the given steps to set up HTTP:
  • Installing certbot
  • Installing certbot
  • Generating the SSL certificate by Certbot
  • Allowing Express to serve the static files
  • Confirming the domain
  • Obtaining the certificate
  • Setting up the renewal.
Answer: The options available are given below:
  • –sessions or –s
  • –sessions or –s for adding session report
  • –hogan or –H
  • –hogan or –H for adding Hogan.js engine support
  • –ejs or –e for adding EJS engine support
  • –css or –c for adding style sheet support
  • -jshtml or –J for adding JSHTML engine support
  • –force or –f for forcing app generation on the directory which is non-empty.
Answer: The server is used to initialize the Middleware, routes, and other application logic. In contrast, the app comprises all the business logic that will be served by the server-initiated routes. This permits the encapsulation of the business logic from the application logic for smooth functioning.
Answer: Debugging is a vital aspect of software development, and both Linux and Windows provide various tools to facilitate this. In the context of Express JS, you can use the following methods to debug your application:
  • Console.log: This is the simplest way to debug an Express JS application. You can output messages to the console which can be viewed in the terminal. This method works on both Linux and Windows systems.
  • Node Inspector: Node Inspector is a powerful tool that allows you to debug your Node.js applications using Chrome Developer Tools. It supports features like setting breakpoints, stepping over functions, and inspecting variables.
  • Visual Studio Code Debugger: Visual Studio Code provides a built-in debugger that works on both Linux and Windows. It supports advanced features like conditional breakpoints, function breakpoints, and logpoints.
  • Utilizing debug module: Utilizing debug module: The debug module is a small Node.js debugging utility that allows you to create debugging scopes. It works by default on both Linux and Windows. To debug an Express application using the debug module, you would first need to set the DEBUG environment variable. For example: DEBUG=express would enable debugging for all modules under Express.
Answer: Express application generator helps to quickly create an application skeleton. The given command is used to install the express application generator. npm install expr ess-generator –g express myApp

Leave a Reply

Your email address will not be published. Required fields are marked *