Case Studies web

NodeJs Interview Questions Answer

NodeJs Interview Questions Answer

February 8, 2023
Case Studies ,web

Q1: What is Node.js?

Answer: As an asynchronous event-driven JavaScript runtime, Node.js is designed to build scalable network applications. In the following “hello world” example, many connections can be handled concurrently. Upon each connection, the callback is fired, but if there is no work to be done, Node.js will sleep.
const http = require('http');
const hostname = '';
const port = 3000;

const server = http.createServer((req, res) => {
res.statusCode = 200;
res.setHeader('Content-Type', 'text/plain');
res.end('Hello World');

server.listen(port, hostname, () => {
console.log(`Server running at http://${hostname}:${port}/`);

Q2: What Can Node.js Do??


  1. Node.js can generate dynamic page content
  2. Node.js can create, open, read, write, delete, and close files on the server
  3. Node.js can collect form data
  4. Node.js can add, delete, modify data in your database

Q3: What are the two types of API functions in Node.js?

Answer: The two types of API functions in Node.js are:

  1. Asynchronous, non-blocking functions
  2. Synchronous, blocking functions

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    Q4: What are the key features of Node.js?

    Answer: Following are main benefits of using Node.js

    1. Asynchronous event driven IO helps concurrent request handling – All APIs of Node.js library are aynchronous that is non-blocking. It essentially means a Node.js based server never waits for a API to return data. Server moves to next API after calling it and a notification mechanism of Events of Node.js helps server to get response from the previous API call.
    2. Very Fast – Being built on Google Chrome’s V8 JavaScript Engine, Node.js library is very fast in code execution.
    3. Single Threaded but highly Scalable – Node.js uses a single threaded model with event looping. Event mechanism helps server to respond in a non-bloking ways and makes server highly scalable as opposed to traditional servers which create limited threads to handle requests. Node.js uses a single threaded program and same program can services much larger number of requests than traditional server like Apache HTTP Server.
    4. No Buffering – Node.js applications never buffer any data. These applications simply output the data in chunks.
    5. Node.js library uses JavaScript – This is another important aspect of Node.js from the developer’s point of view. The majority of developers are already well-versed in JavaScript. Hence, development in Node.js becomes easier for a developer who knows JavaScript.
    6. There is an Active and vibrant community for the Node.js framework – The active community always keeps the framework updated with the latest trends in the web development.

    Q5: What are the core modules of Node.js?


    1. EventEmitter
    2. Stream
    3. FS
    4. Net
    5. Global Objects

    Q6: What is V8?

    Answer: The V8 library provides Node.js with a JavaScript engine (a program that converts Javascript code into lower level or machine code that microprocessors can understand), which Node.js controls via the V8 C++ API. V8 is maintained by Google, for use in Chrome.
    The Chrome V8 engine :

    1. The V8 engine is written in C++ and used in Chrome and Nodejs.
    2. It implements ECMAScript as specified in ECMA-262.
    3. The V8 engine can run standalone we can embed it with our own C++ program.

    Q7: What is an error-first callback?

    Answer: Error-first callbacks are used to pass errors and data. The first argument is always an error object that the programmer has to check if something went wrong. Additional arguments are used to pass data.
    fs.readFile(filePath, function(err, data) {
    if (err) {
    //handle the error
    // use the data object

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