The 10 Most Important Node.js & Express.js Interview Questions You Need To Know In 2023 (5 Easy, 3 Medium, 2 Hard)/

Node.js and Express.js are popular frameworks for building web applications and APIs. If you’re preparing for a Node.js or Express.js interview, here are ten important interview questions to consider, ranging from easy to hard.

5 Easy Node.js & Express.js Interview Questions

1. What is Node.js, and how is it different from other server-side technologies?
   Node.js is an open-source, cross-platform JavaScript runtime environment that is used for building server-side applications. Node.js is different from other server-side technologies because it is based on JavaScript and allows developers to use the same language on both the client and server-side.
2. What is middleware in Express.js, and how is it used?
   Middleware is a function in Express.js that sits between the request and response objects and can perform various tasks, such as logging, authentication, and error handling. Middleware is used to modify the request or response objects, add data to the request object, or perform other tasks before the request is handled by the application.
3. What is the purpose of the Node.js event loop, and how does it work?
   The Node.js event loop is a mechanism for handling asynchronous operations in Node.js applications. The event loop allows Node.js to handle multiple requests and operations at the same time by running them in parallel and asynchronously. The event loop works by maintaining a queue of operations and executing them in a loop, checking for new operations each time the loop runs.
4. What is the difference between the HTTP GET and POST methods in Express.js?
   In Express.js, the HTTP GET method is used to retrieve data from the server, while the HTTP POST method is used to send data to the server. The GET method is used for read-only operations, such as retrieving data from a database, while the POST method is used for creating or updating data on the server.
5. What is the purpose of the Node.js module system, and how is it used?
   The Node.js module system is a way to organize and reuse code in Node.js applications. The module system allows developers to create and export modules that can be used in other parts of the application. Modules can be shared between different parts of the application or between different applications.

… 3 Medium Difficulty Node.js & Express.js Interview Questions …

6. What is the purpose of the Express.js router, and how is it used?
   The Express.js router is a built-in middleware that provides a way to handle different routes and URLs in an Express.js application. The router allows developers to define specific routes for different requests and to handle different types of requests, such as GET, POST, and DELETE.
7. What is the purpose of the Node.js package.json file, and how is it used?
   The package.json file is a configuration file in Node.js applications that provides information about the application, its dependencies, and its scripts. The package.json file is used by NPM to install, manage, and update packages and dependencies for the application.
8. What is the difference between Node.js’ child processes and worker threads?
   Node.js provides two mechanisms for handling parallel processing: child processes and worker threads. Child processes are separate processes that are run independently of the main Node.js process, while worker threads are threads that run within the Node.js process. Child processes are better suited for heavy computational tasks, while worker threads are better suited for I/O operations.

… And Finally, 2 Hard Node.js & Express.js Interview Questions

9. What is the purpose of the Node.js REPL, and how is it used? The Node.js REPL (Read-Evaluate-Print-Loop) is an interactive console that allows developers to test and experiment with Node.js code. The REPL allows developers to write and execute Node.js code in real-time, making it a useful tool for debugging and testing. Developers can use the REPL to experiment with Node.js code, test different functions, and explore different parts of the Node.js environment.
10. What is the purpose of Express.js’ view engine, and how is it used to render views?
    Express.js provides a built-in view engine that allows developers to render dynamic views in response to HTTP requests. The view engine uses templates and data to generate HTML that is sent back to the client. Developers can choose from a variety of view engines, such as Pug or Handlebars, to render their views. The view engine is a powerful tool for building dynamic and responsive web applications, and by understanding how to use it, developers can create engaging and visually appealing user interfaces.

Final Words

Node.js and Express.js are popular frameworks for building web applications and APIs, and being proficient in these technologies can be a valuable asset for a developer. In this article, we covered ten important Node.js and Express.js interview questions that you may encounter in a job interview, ranging from easy to hard.

To succeed in a Node.js or Express.js interview, it’s essential to understand the basics of Node.js, including the Node.js event loop, modules, and child processes, and the basics of Express.js, including middleware, routing, and view engines. It’s also important to be familiar with more advanced concepts, such as clustering, the package.json file, and the REPL.

Node.js and Express.js offer unique features that make them powerful frameworks for building web applications and APIs. Node.js allows developers to use JavaScript on the server-side, while Express.js provides a powerful set of features and tools for building web applications and APIs. By understanding the key concepts and features of Node.js and Express.js, developers can set themselves apart as skilled and valuable contributors to any development team.