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Node JS Interview Questions And Answers

Q) Node JS Vs Ruby

Feature Node JS Ruby On Rails
Written In C, C++, JavaScript Ruby
Operating System Solaris, OpenBSD,  FreeBSD, Linux, Mac, MS, webOS and nonStopOS Cross-Platform
Type Event driven networking Web application framework
License MIT MIT
Performance High Low
Popularity Popular for its features Yet to be popular
Documentation Available Lack of documentation
Concistency Inconsistent Consistent structure
Complexity Easy to implement Complex implementation


Q1) What is NodeJS?

Ans: Node.js can be simply explained as it is a concept of two outcomes: runtime environment and JavaScript library. So basically, node.js will enable you to use javascript beyond the browser. It can make Javascript like 'go anywhere Javascript'.

Q2) What is NPM?

Ans: Javascript operates in a runtime environment with the help of node js having its own package manager, this package manager is called as NPM.

Q3) Explain CLI in Node.js?

Ans: One of the vital reasons for Node.js getting popular is it's 900000 packages connected to a large ecosystem. CLI that is a command-line interface will allow you to automate your tasks by taking advantage of this vast ecosystem. Not only that, by writing CLI you can differentiate your proposed packages among the ecosystem.

Q4) In which Language Node Js is written?

Ans: Node.js shows compatibility with three types of language 

  1. C
  2. C++
  3. Javascript 

Q5) Who is the author of Node Js?

Ans: Ryan Dahl is author of Node.js it was almost 13 years back when javascript environment was introduced to the world. Initially, Node is was supported by Linux and Mac OS X but later it was sponsored by Joyent.

Q6) Explain What is a Javascript Engine?

Ans: Javascript engine is used to run the java code in the browser so you can define a javascript engine as a computer program which is used to perform the java code. Initially, it was just used for interpretation and progressively it improved and got evolved. Generally, all browsers have one dealer and he is the one who develops the javascript engine.

Q7) Explain V8 Engine?

Ans: In 2008 when google chrome was launched at that time chrome also introduced its project of the V8 engine. It is an open-source network which can be written in c++ language.

Q8) Explain ECMAScript?

Ans: Ecmascript first appeared in 1997, which was specified and developed by Esma internationals. Evmascriot is also a programming language, which developed various other scripts like Jscript, ActionScript and the most popularly used javascript.

Q9) How can you check the installed version of Node Js?

Ans: For that, you need to install NPM which is a package manager. The second thing you will need is to have a node in your computer, you can check installed NPM and node by just typing simple commands. Now carry the following steps

  • Open the windows command prompt
  • Open command-line tool line Babun, Powershell, ConEmu etc.
  • Type node-v which will display your current version of Node Js.

Q10) Explain Modules in Node Js?

Ans: Modulus is various commands used in node js to perform tasks like addition, subtraction, division, multiplication etc. Ins short you can do maths in js using modulus.

Q11) What are the common Modules?

Ans: Arithmetic operations ( addition, subtraction, multiplication, division), exponentials, increment and decrement are various common modulus in js.

Q12) For what require() is used in Node Js?

Ans: Modulus is operated by two main managing modules 

  • The Require module
  • The module module

Both of them are available on the global scope.

Q13) Explain module.exports in Node Js?

Ans: The module.exports is a default application which can be found in every js file of Node js.

Q14) Is Node Js Single-threaded?

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Ans: Node Js is single-threaded but it is non-blocking as well, it means that while operating node js various functions like callbacks is carried out in the background which is carried out using different threads or multiple threads.

Q15) What are the events?

Ans: The event can be explained as activities carried out. For example, when you open a file it is an event when close a file it is an event.

In Node js, there is a defaulted module named as "Events" with which you can carry various activities like create, fire, listen etc.

Q16) Explain the event loop in Node Js?

Ans: Non-blocking operations in Node Js are carried out with the help of the event loop.

Q17) How to create a simple server in Node js that returns Hello World?

Ans: Certain steps are needed to be carried out for this operation:

  • Import the module which is required.
  • Create the server using HTTP.createServer().
  • Test the request and wait for a response 

Q18) Difference between the cluster and child_process modules?

Ans: Cluster is when one master programme is running two or more nodes at a single running time.

A child process simply starts a new script on the system, it is quite similar to the cluster but in a different language.

Q19) How to stop the master process without suspending all of its child processes?

Ans: Upstart is a process management system with which you can stop the master process. Generally when the master process is stopped or killed the child process still continues to work.

Q20) What does emitter do and what is dispatcher?

Ans: The emitter is one which makes communication between two nodes.

When the job of the scheduler is completed in a program than dispatched comes into the frame and takes the task to the desired status.

Q21) Since the node is a single-threaded process, how to make use of all CPUs?

Ans: The node js is single-threaded but node name itself suggests that it is a topology, that means there is communication between two nodes. This communication between the two nodes makes use of all CPUs.

Q22) Syntax to install modules using NPM.

Ans: Syntax : $ npm install

Example: $ npm install express
var express = (‘express’);
Where express is Name of the module,
express is JS file, that can be used in your module.

Q23) Mention types of npm modules available that are used very often.

Ans: Express, connect, socket.io and socketjs, pug, mongodb and mongojs, redis, lodash, forever, bluebird, moment are some of npm modules.

Q24) Command to list modules installed in current npm

Ans: $ npm ls

Note: Remember not to mention npm in UPPERCASE - (Recommended)

Q25) What are the attributes of package.json

Ans: Name, version, description, homepage, author, contributors, dependencies − list of dependencies, repository − repository type and URL of the package, main − entry point of the package, keywords.

Q26) What is REPL?

Ans: REPL - Read, Eval, Print, Loop.
It is an environment to input commands to perform REPL tasks. Each of the task is associated with its respective operations.

Q27) What kind of applications can be built by Node.JS.

Ans: DIRT, JSON, I/O Bound, Single Page applications are preferable to use Node.JS.

Q28) What is the latest version of Node JS.

Ans: Node v8.0.0 is the current version.

Q29) NodeJS is a framework. True or False.

Ans: False. It is runtime or environment, but not a framework.
 

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Q30) Commands to work with the file from the local database.

Ans: Var fs = require(‘fs’);

  • Read: fs.readFile();
  • Create:
    • fs.appendFile();
    • fs.open();
    • fs.writeFile();
  • Write: fs. writeFile();
  • Delete: fs.unlink();
  • Rename: fs.rename();
  • Update:
    • fs.appendFile()
    • fs.writeFile()

Q31) What is error-first callback in Node JS?

Ans: In order to check for proper working of the code, we need to verify error free execution. In this regard, error-first callbacks are used, that will send error first, followed by related data to the error.

Q32) What is cluster?

Ans: Cluster is a process to handle thread execution load while working with multi-core systems.

Q33) Why node is single threaded?

Ans: In order to upgrade the performance well, single thread operations work better than multi-threaded operations. 

Q34) How does URL module works.

Ans: This module helps URL to parse it into host, pathname, search, query, etc.

Example:

var url = require('url');
var adr = 'https://mindmajix.com/?s=node+js+training';
var q = url.parse(adr, true);
console.log(q.host); //returns 'mindmajix.com'
console.log(q.search); //returns '?s=node+js+training'

Q35) Explain use of nodemailer module.

Ans: It is not included in default modules list, it has to be installed using npm.
Var nodemailer = require(‘nodemailer’);

Q36) What are the types of versions available?

Ans: Patch_Version, Minor_Version, Major_Version.

Q37) What are event emitters in NodeJS?

Ans: Objects in NodeJS will have to trigger events in order to maintain asynchronous execution of core API used. These objects that emit events are known as Event Emitters.

Q38) What are event listeners?

Ans: Events that are emitted by event emitters have to be listened in order to continue the asynchronous execution of the threads. These objects that listens the emitted events are known as listeners.

Bottom Line

When you are going for an interview go through all these basic questions at least once.

If you are well prepared and know basic things related to node js you can be confident while facing the interviewer. 

Always try to question each and everything you know about programming and find its answer. If you can explain it to yourself then you are well prepared and your concepts are clear. Comment below your experience of the interview and if you had been before for an interview which questions we're asked that are not mentioned above. let us know and we will find the answer to that question for you.

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