Top Node.js Interview Questions and Answers

Here are top nodejs interview questions,

1. What is Node.js?

Node.js is an open-source, server-side JavaScript runtime environment that allows developers to build scalable and high-performance network applications.

 

 

2. What is the difference between Node.js and JavaScript?

JavaScript is a programming language, while Node.js is a runtime environment that allows you to run JavaScript on the server-side.

 

3. What is an event-driven programming paradigm in Node.js?

Event-driven programming is a programming paradigm in which the flow of the program is determined by events, such as user actions or system events. In Node.js, it allows non-blocking I/O operations and improves scalability.

 

4. What is NPM?

NPM (Node Package Manager) is the default package manager for Node.js. It provides a registry of reusable JavaScript packages/modules that can be easily installed, updated, and managed in Node.js projects.

 

5. What is a module in Node.js?

In Node.js, a module is a reusable block of code that encapsulates related functionality. It can be imported into other modules using the 'require' keyword.

 

6. What is the 'require' function in Node.js?

The 'require' function is used to include modules in Node.js. It loads and executes the specified module and returns its exports object.

7. What is the difference between 'require' and 'import' in Node.js?

'require' is a CommonJS module system syntax used in Node.js, while 'import' is an ES6 module syntax used in modern JavaScript. 'require' is synchronous, while 'import' is asynchronous and requires a transpiler like Babel to work in Node.js.

 

8. What is the purpose of the 'package.json' file?

The 'package.json' file is a metadata file in Node.js projects that contains information about the project, including its dependencies, scripts, version, and more. It is used by NPM to manage the project and its dependencies.

 

9. What is the difference between 'npm install' and 'npm ci'?

'npm install' installs the dependencies listed in the 'package.json' file, while 'npm ci' installs the exact versions of the dependencies specified in the 'package-lock.json' or 'npm-shrinkwrap.json' file. 'npm ci' is typically used in continuous integration and deployment environments.

 

10. What is callback hell? How can it be avoided?

Callback hell refers to the situation when multiple nested callbacks are used, leading to unreadable and hard-to-maintain code. It can be avoided by using promises, async/await, or using control flow libraries like Async.js or Bluebird.

 

11. What is the purpose of the 'exports' object in Node.js modules?

The 'exports' object in Node.js modules is used to expose the module's functionality to other modules. It allows you to define the public API of the module.

 

12. What are streams in Node.js?

Streams in Node.js provide a way to handle data in chunks and process it asynchronously. They are used for reading from or writing to large files or network sockets without loading the entire data into memory.

 

13. What is middleware in the context of Node.js and Express.js?

Middleware in Node.js and Express.js are functions that have access to the request and response objects in the application's request-response cycle. They can perform operations, modify requests or responses, and pass control to the next middleware in the chain.

 

14. What is the purpose of the 'module.exports' object in Node.js?

The 'module.exports' object is used to define the public API of a Node.js module. It allows you to export variables, functions, or objects from the module to be used in other modules.

 

15. What is the purpose of the 'process' object in Node.js?

The 'process' object in Node.js provides information and control over the current Node.js process. It provides various properties and methods to interact with the process, such as 'process.env', 'process.argv', and 'process.exit()'.

 

16. What is clustering in Node.js?

Clustering in Node.js allows you to create multiple instances of the Node.js process to take advantage of multi-core systems. It improves application performance and scalability by distributing the workload across multiple cores.

 

17. What is a promise in Node.js?

A promise in Node.js is an object that represents the eventual completion or failure of an asynchronous operation. It allows you to write asynchronous code in a more readable and manageable way.

 

18. What is error-first callback in Node.js?

Error-first callbacks are a convention in Node.js where the first argument of a callback function is reserved for an error object. If the operation is successful, the error object will be null or undefined. It helps in handling errors in an asynchronous code flow.

 

19. What is REPL in Node.js?

REPL (Read-Eval-Print Loop) is an interactive shell available in Node.js that allows you to experiment, test, and execute JavaScript code snippets. It stands for the ability to read user input, evaluate it, print the result, and loop back to read the next input.

 

20. What is the difference between 'process.nextTick()' and 'setImmediate()' in Node.js?

'process.nextTick()' and 'setImmediate()' are used to schedule the execution of a callback function in the next iteration of the event loop. The main difference is that 'process.nextTick()' executes the callback immediately after the current operation, before I/O events, while 'setImmediate()' executes the callback before the next I/O event.

Above are few top nodejs interview questions. Remember to prepare and expand on these answers.

Good luck with your interview!  👍