Nodejs Backend Developer Interview Questions

11. What is Node.js and how it works?

Node.js is a JavaScript runtime environment that allows developers to run JavaScript code outside of a web browser. It uses the V8 JavaScript engine, which is the same engine used by Google Chrome, to execute JavaScript code on the server-side.

Node.js works by providing an event-driven, non-blocking I/O model that allows for highly efficient and scalable server-side applications. It utilizes asynchronous programming techniques to handle multiple requests simultaneously without blocking the execution of other code. Node.js is particularly well-suited for building real-time web applications, APIs, and microservices. It also comes with a vast ecosystem of libraries and frameworks that extend its capabilities for various use cases.

12. How do you manage packages in your node.js project?

Modules are the blocks of reusable code consisting of Javascript functions and objects which communicate with external applications based on functionality. A package is often confused with modules, but it is simply a collection of modules (libraries).

13. How can we use async await in node.js?

To use async await in Nodejs:

• Define an asynchronous function with the async keyword.
• Use the await keyword within the function to pause execution until promises are resolved.
• Handle errors using try/catch blocks.
• Call the asynchronous function and use await to wait for its result.

Example: After async/await

async function fun1(req, res){
  let response = await request.get('http://localhost:3000');
    if (response.err) { console.log('error');}
    else { console.log('fetched response');
}

14. What is node.js streams?

Streams are one of the fundamental concepts of Node.js. Streams are a type of data-handling methods and are used to read or write input into output sequentially. Streams are used to handle reading/writing files or exchanging information in an efficient way.

Accessing Streams:

const stream = require('stream');
const fs = require("fs");
const readablestream = fs.createReadStream("source.txt"); // the txt file in which data is available
const writeablestream = fs.createWriteStream("destination.txt"); // the txt to which we want to copy the data
readablestream.pipe(writeablestream);
readablestream.on("error" , (err)=>{
console.log(err); // this will handle the error due to source.txt(if any error will be place)
}
writeablestream.on("error" , (err)=>{
console.log(err);// this will handle the error due to source.txt(if any error will be place)
}
writeablestream.on("finish" ,  ()=>{
console.log("data from source.txt is successfully copied to destination.txt"); 
}

15. Describe the exit codes of Node.js?

Node.js is a cross-platform, open-source back-end JavaScript runtime environment that uses the V8 engine to execute JavaScript code outside of a web browser. Exit codes in Node.js are a specific group of codes that finish off processes, which can include global objects as well.

16. Explain the concept of stub in Node.js?

A small program routine that substitutes for a longer program which is possible to be loaded later or that is remotely located.

Features of stub:

• Stubs can be either anonymous.
• Stubs can be wrapped into existing functions. When we wrap a stub into the existing function the original function is not called.

17. Enhancing Node.js performance through clustering.

Clustering is the process through which we can use multiple cores of our central processing unit at the same time with the help of Node JS, which helps to increase the performance of the software and also reduces its time load.

We can install cluster modules through the given command.

npm i cluster

18. What is WASI and why is it being introduced?

WASI also called as Web assembly system interface , it is like a bridge between operating system and web assembly , let me explain Web Assembly , see the browser only understand javascript so if any user sends a c++ or rust code on the browser so for translating that code web assembly is used , so web Assembly is like a translator which convert one language of code to the other.

so WASI provides a standard way to talk to the outside world like operating system so that so that it can ask to read the file or perform the other operations .

19. How to measure the duration of async operations?

Asynchronous operation in Node.js is a non-blocking operation which means if we perform an asynchronous operation at a certain point in code then the code after that is executed and does not wait for this asynchronous operation to complete.

Syntax:

const calcTime = async () => {
  const start = Date.now();
  await someAsyncOperation();
  const end = Date.now()
  const duration = end - start;
}

20. What is a thread pool and which library handles it in Node.js?

A thread pool is a collection of worker threads that are used to execute asynchronous tasks concurrently in a multithreaded environment. Each task is assigned to a worker thread from the pool, allowing for efficient parallel execution of tasks without creating a new thread for each task.

In Node.js, the libuv library handles the thread pool. libuv is a cross-platform library responsible for asynchronous I/O operations, including file system operations, network operations, and timers. It manages the thread pool to handle these asynchronous tasks efficiently.

Backend development involves working on the server side of web applications, where the logic, database interactions, and server management take place. It focuses on handling data, processing requests from clients, and generating appropriate responses.

In this Top Backend Development interview questions, We cover Interview questions from all important topics from basic to advanced such as JavaScript, Node.js, Express.js, SQL, MongoDB, Django, PHP, Java Spring, and API. No matter whether you are a fresher or an experienced professional we have got questions that will enhance your skills and help you shine in your backend development interview.