Node js Interview Questions

The top Node.js interview questions are right here! These expert-curated Node.js interview questions and answers will boost your knowledge and confidence in a short period of time. We have compiled a list of basic and advanced Node.js interview questions that discusses the basics of Node.js, its features, npm and its components, etc. Be prepared and get recruited by your dream employer as a Node.js developer, front end developer, and other interesting profiles.

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Beginner

  1.  A server side platform built on Google Chrome’s Javascript V8 Engine.
  2. Open source, cross platform runtime environment for developing server side and networking applications. Node.js runs on various platforms like Windows, Linux, MacOs.

For those coming from Java development background , here is the analogy.

It is not advisable to use Node.js for CPU intensive applications

Because node.js is designed around using a single thread very efficiently. Its event based model dispatches code fragments when specific events occur. Those code fragments are supposed to execute very quickly and then return control to node.js, which then dispatches the next event.

If one of those code fragments performs a long running task, then no more events will be dispatched and the whole system appears to hang.

Microsoft, Paypal, Uber

Microsoft Visual Studio code uses Node.Js as a platform.

Paypal migrated their application from Java backend to Node.JS and achieved benefits like increased productivity and lesser lines of written code and fewer files are constructed.

Uber was among the first to put Node.js into full production. Its mobile application process needed high scalability option due to increasing demand of users. Uber’s Despatching system runs on Node.JS. Uber achieved benefits like faster code deployment and effective error analysis(without restart) and high scalability.

Here is the list of important features of Node.JS

No buffering: Node.js applications never buffer any data(ASCII). These applications simply output data in chunks.

Extremely Fast: Node.js is built on Google Chrome’s Javascript V8 Engine so its library is very fast in code execution. As you are aware Javascript is used to built client side applications which is also built on V8 engine, so this makes Node JS applications faster.

I/O is Asynchronous and Event Driven: All APIs of Node.js library are asynchronous i.e. non-blocking. So a Node.js based server never waits for an API to return data. The server moves to the next API after calling it and a notification mechanism of Events of Node.js helps the server to get a response from the previous API call. It is also a reason that makes it is very fast

Highly Scalable: Node.js is highly scalable because event mechanism helps the server to respond in a non-blocking way.

  1. I/O bound applications.
    It can be anything ranging from reading/writing local files to making an HTTP request to  an API. 
  2. Data streaming applications.
    Stock broker trading applications – takes those prices and send them in realtime to    customers or to other application for further processing.
  3. Data intensive Real time applications. Like Chat applications like Whatsapp, facebook,  Linkedin
  4. JSON API based applications like Twitter
  5. Single page applications like Angular applications.
    Angular uses npm (NodeJS package manager) for accessing its libraries. For speeding  up angular development you need CLI (Command level Interface)which inturn requires  node and npm.

Streams are a way handling following:

  1. reading/ writing files
  2. network communications
  3. any kind of end-to-end information exchange.

It is the movement of data from one point to another.

When a program is supposed to read a file consisting of single page(three to four lines), it will be initially read into memory from start to finish and then starts processing. If the file is an e-book consisting of 500+ pages , then it takes lot of storage space and time to be loaded into memory, before started processing. This is where Streams make a difference.

Using streams, you read it piece by piece , processing its content without keeping it in memory.

The following are the advantages of streams

  1. Memory Efficiency: You don’t load large amounts data before processing it, It just reads a block of data and process it immediately and continues the same till end of the file.
  2. Time Efficiency: It takes way less time to process the data as soon as you have it without having to wait for whole data to be loaded or available.

The following code statement refer to stream module

const stream = require(‘Stream’);

The following are the types of streams in Node.Js:

1) Readable Streams: A stream where you can recieve data but cannot send it.  When you push data into a readable stream , it is buffered, until customer starts to read the data

    Example: HTTP Requests to the server. Based on the HTTP request, server sends HTTP response to the client which is a readable stream. Another example is RSS feed posted by remote servers on the HTTP clients are readonly streams.

Module used: fs.createReadStream

2) Writable Streams: A stream where you can send the data but not recieve  from it.

    Example: user entered data on HTTP clients go as HTTP Responses to the server where data is written.

Module used: fs.createWriteStream()

3) Duplex Streams: Streams that are both readable and writable.

Example: TCP sockets

Module used: net.socket

4) Transform Streams: A type of duplex streams where output is in someway related to the input. Like duplex streams, Transform streams also implement both Readable and Writable interfaces.

Node.js is a javascript server environment built on Google Chrome’s Javascript engine(V8 Engine). It’s very well suited for highly scalable I/O intensive web applications, real-time web applications and network applications. Node.js is the server side technology for the MEAN stack which is one of the most popular software stack for building dynamic web sites and web applications .Node.js is open source and hence has great community support. Main features of Node.js are

  1. All API’s could be made asynchronous providing greater concurrency. This means that Node.js server never waits for API to return data.
  2. Node.js is comparatively faster than other server-side scripting tools as it uses the V8 javascript engine.
  3. It follows a single threaded event loop model architecture where all client requests are executed on the same thread. Event looping helps node.js servers to work in a non-blocking (without waiting for API calls to finish to cater to another API call)manner that in turn increases the scalability of the system.
  4. No buffering happens in node.js that means all data is provided in chunks as output.

Node.js is often not preferred with relational database and CPU intensive applications.

Npm or Node Package Manager is the default package manager for Node.js.It works as:

  1. An online repository called as npm registry used for the open-source Node.js projects.npm registry is a large database with around half a million packages. Developers can download from and publish packages to the npm registry.
  2. Npm is also a  command-line utility for interacting with an online repository that helps in package installation, version management, and dependency management.

Few of the important  npm commands are:

  • Any package can be installed  by running a simple command

“ npm install <name of the package> “.

This will install the module under the path, “./node_modules/”. Once installed the module could be used just like they were built-ins. Dependency management could also be done with npm. Our node project will have a package.json which will have all the dependencies needed for our project. If we perform “npm install” from project root all the dependencies listed in the package.json file will be installed.

  • “npm init” Here package.json file is created that is where all dependencies are included.
  • “npm update <package_name>”  where the specific package is updated with new features
  • “npm uninstall <package_name>” where the specific package is uninstalled. It’s then removed from the “node_modules” folder.
  • “npm list” is used to list all the packages installed.
  • npm help” is the built-in help command.To get help for a particular command, use

“npm <command> -h”

A callback function is called at the end of a specific task or simply when another function has finished executing. Callback functions are used exclusively to support the asynchronous feature or non-blocking feature of Node.js. In the asynchronous programming with Node.js, servers don’t wait for any action like API call to complete to start a new API call.

For eg

Let’s  read a file say “input.txt” and print its output in the console.The synchronous or blocking code for the above requirement is shown below:

var fs = require("fs");
var data = fs.readFileSync('input.txt');  // execution stops and waits for the read to finish
console.log(data.toString());
console.log("Program Ended"); 
Let’s rephrase the code with the callback function.
var fs = require("fs");
fs.readFile('input.txt', function (err, data) {
   if (err) return console.error(err);
   console.log(data.toString());
});
console.log("Program Ended");

Here program does not wait for reading the file to complete but proceeds to print "Program Ended".If an error occurs during the read function readFile(), err object will contain the corresponding error and if the read is successful data object will contain the contents of the file. readFile() passes err and data object to the callback function after the read operation is complete, which finally prints the content.

Pyramid of Doom or Callback hell happens when the node.js programs are very complex in nature and having heavily nested callback functions. The name is attained by the pattern caused by nested callbacks which are unreadable.

For eg

Let’s assume that we have 3 different asynchronous tasks and each one depends on the previous result causing a mess in our code.

asyncFuncA(function(x){  
         asyncFuncB(x, function(y){ 
                asyncFuncC(y, function(z){ 
                    ...
                });
            });
      });

Callback hell could be avoided by the following methods :

  • Handling all errors immediately
  • Splitting the callbacks into smaller and independent functions
  • Declaring callback functions beforehand.
  • Libraries like Async.js adds a layer of functions on top of your code reducing the complexity of nested callbacks.
  • Usage of Promises where async code could be written that handles errors due by the usage of try/catch-style error handling.

There are two types of API functions available in Node.js:

1.Synchronous or Blocking functions where all other code execution is blocked till an I/O event that is being waited on completes. These are executed synchronously one after the other.

For eg: 

Reading a file called ‘file.txt’

const fs = require('fs');
const data = fs.readFileSync('file.txt’); // blocks here until file is read

Here the execution of further lines in the program will be blocked. If any error is thrown it needs to be caught immediately to avoid the crashing of the program.readFileSync() completely reads the content to the memory and then prints the data in the console. The blocking function has an adverse effect on the application’s performance.

2.Asynchronous or Non-blocking functions are another type of API functions where multiple I/O calls can be performed without the execution of the program being blocked.

For eg: 

Reading a file “file.txt”

const fs = require('fs');
fs.readFile('file.txt’, function(err, data) => {
  if (err) throw err;
 });

Here reading of the file (readFile()) doesn’t block further execution of the next instruction in the program. The above function takes the file name and passes the data of the file as a reference to the callback handler. Then the file system object remains ready to take up any other file system operation. Asynchronous API functions increase the throughput by increasing the number of instructions handled per cycle time.

Streams are abstract interface available with Node.js.The stream module helps in implementation of streaming data. There are four types of streams.

  • <Readable> for the reading operation
  • <Writable> for the writing operation
  • <Duplex> for both reading and writing operations
  • <Transform> is a derived from Duplex stream that computes available input.

The important events on a readable stream are:

  • The data event, where the stream passes a chunk of data to the consumer.
  • The end event, which happens when there is no more data to be used from the stream.

For eg:

Reading a file “input.txt”

var fs = require('fs');
var readableStream = fs.createReadStream('input.txt'); // creates readable stream                  var data = '';
readableStream.on('data', function(txt) {    // data event produces the flow of data
    data+=txt;
});
readableStream.on('end', function()  // end event is triggered when no data to read
{
    console.log(data);
});

The important events on a writable stream are:

  • The write event, that signals that the writable stream can receive more data.
  • The finish event, that is produced when all data has been written to the underlying system.

For eg:

Write “Hello World “ to file.txt

var fs = require("fs");
var data = 'Hello world';
var writerStream = fs.createWriteStream('file.txt');  // Create a writable stream
writerStream.write(data,'UTF8'); // Write the data to stream 
// Mark the end of file
writerStream.end();
writerStream.on('finish', function() {  // finish triggered when all data is written to 
   console.log("Write completed.");
});

Piping the streams is one of the most popular mechanisms in Node.js programs where output of one stream is provided as the input to another stream.For eg:

var fs = require("fs");
var readerStream = fs.createReadStream('example.txt'); // Readable stream
var writerStream = fs.createWriteStream('exampleOutput.txt'); // Writable stream
readerStream.pipe(writerStream);// Pipe the readable stream as input to writable stream
console.log("Program Ended");

REPL module in Node.js is Read-Eval-Print-Loop (REPL) implementation. It’s just like a shell and command prompt.REPL is available both as a standalone program or included in other applications. It can be accessed using the command:

“const repl = require('repl');”

REPL accept individual lines of user input, evaluate them and then output the result. Input and output use stdin and stdout, respectively, or use any Node.js stream.REPL is mainly used for testing, debugging, or experimenting as it helps to execute ad-hoc javascript statements. The repl module exports the “repl.REPLServer” class which supports automatic completion of multi-line inputs, Emacs-style line editing,  ANSI-styled output, saving and restoring current REPL session state, error recovery, and customizable evaluation functions. REPL environment could be started by the opening terminal in case of Unix/Linux or command prompt in case of windows and typing “node”. Some of the commands supported by the REPL environment are below:

  • .break - In case of a multi-line expression, entering the .break command (or pressing the <ctrl>-C key combination) will abort further processing of the expression.
  • .clear - Reset  the REPL to an empty object
  • .exit - Causes the REPL to exit.
  • .help - Show the list of commands.
  • .save filename - Save the current REPL session to a file.
  • .load filename - Load a file into the current REPL session.
  • .editor - Enter REPL into editor mode (<Ctrl>-D to finish, <ctrl>-C to cancel).

Test pyramid is the pictorial representation of the ratio of unit tests, integration tests and end-to-end tests required for developing a good quality node.js project.

  • Usually, a large number of low-level unit tests are written.
  • Comparatively less number of integration tests are written that tests how modules interact with each other.
  • Fewer end-to-end tests are written that tests the system as a whole.

Unit tests help to check the working of a single component or module. All dependencies are stubbed providing tests for exposed methods. Modules used for Node.js Unit Testing are:

  • Test runners like Mocha
  • Assertion library like Chai
  • Test spies, stubs and mocks like Sinon

Some of the above tools could also be used for integration tests for eg: SuperTest, Mocha and Chai that detects the defects in the early stage itself. Integration tests run faster than end-to-end tests.

Testing your application through its user interface is the most popular end-to-end way of testing for any application. End-to-end tests provide us with confidence that our system works all well together. The main disadvantage of end to end testing is that it requires a lot of maintenance and run pretty slowly.

Promises in simple words could be explained as advanced call back functions. Whenever multiple callback functions needed to be nested together Promises could be used. Promises avoid the callback hell produced by nesting together many callback functions. A promise could take up three states defined by the 'then clause'. Fulfilled state, rejected state, and pending state which is the initial state of promise.

Let’s take the example of reading a file and parsing it as JSON

1.Synchronous method of writing the code

function readJSONSync(filename) {
  return JSON.parse(fs.readFileSync(filename, 'utf8'));
}

2.Asynchronous method of writing the code using callback. Introducing callbacks make all I/O functions asynchronous.

function readJSON(filename, callback){
  fs.readFile(filename, 'utf8', function (err, res){
    if (err) return callback(err);
    callback(null, JSON.parse(res));
  });
}

Here a callback parameter confuses a bit so we replace it with promise

3.Implementation Using Promise

function readFile(filename, enc){
  return new Promise(function (fulfill, reject){
    fs.readFile(filename, enc, function (err, res){
      if (err) reject(err);
      else fulfill(res);
    });
  });
}

Here we use “new Promise” to construct the promise and pass a function to the constructor with two arguments. The first one fulfills the promise and the second one rejects the promise.

To start working with promises we need to install the “promise” module first using the command

“npm install promise”  

libuv is a multi-platform library of Node.js that supports asynchronous I/O. It’s written in C.It was developed for Node.js, but it’s also used by Luvit, Julia, pyuv etc.libuv library handles file system, DNS, child processes, pipes, signal handling, polling and streaming.libuv provides the event loop to Node.js.The important features of libuv are:

  • Full-featured event loop
  • Asynchronous TCP & UDP sockets
  • Child processes
  • Thread pool or Worker Pool, that offloads work for some things that cannot be done asynchronously at the OS level.
  • Signal handling

In event-driven programming, an application follows certain events and respond to them when they occur. libuv gathers events from the operating system or other sources of events and then user registers callbacks to be called when an event occurs.

Some examples of events are:

  • The file is ready for writing
  • Time out of a timer

Libuv also provides two types of abstractions to users alongside  These are handles and requests. Handles represent long living objects like TCP server handle where its connection callback is called every time when there is a new connection. Requests are short-lived operations performed on the handle like write requests to write data on a handle.

Node.js follows a single-threaded event loop model architecture. One process in one CPU is not enough to handle the application workload so we create child processes.“child_process” module supports child processes in Node.js. These child processes can communicate with each other using a built-in messaging system. Child processes could be created in four different ways Node: spawn(), fork(), exec(), and execFile().

spawn() method brings up the child processes asynchronously. It is a command designed to run system commands that will be run on its own process. In spawn() no new V8 instance is created and only one copy of your node module is active. When your child process returns a large amount of data to the Node spawn() method could be used.

Syntax:

child_process.spawn(command[, args][, options])

Spawn method returns streams (stdout & stderr) and it’s main advantages are

  • Low memory footprint
  • Handle data in buffered chunks.
  • Evented and non-blocking

In fork() a fresh instance of the V8 engine is created. fork() method could be used as below:

Syntax:

child_process.fork(modulePath[, args][, options])

In fork()  a communication channel is established between parent and child processes and returns an object. We use the EventEmitter module interface to exchange messages between them.

Advanced

npm is world’s largest software repository. Globally, open source developers use npm to share and borrow packages. Example, you need to install node and npm before getting necessary packages for Angular development.Packages are needed to bring modularity to code development.   

npm consists of three distinct components:

  1. website – to discover packages and their dependencies (by searching), setup profiles for authentication, version control management 
  2. CLI (Command line interface) -  runs on a terminal which is the way developers interact with npm.
  3. registry – large public database of javascript software and meta-information surrounding it

Some of the uses of npm are:

  1. manage multiple versions of code and code dependencies
  2. update applications easily when underlying code is updated
  3. Adapt packages of code for your apps, or incorporate packages as they are.

Blocking program 

  1. executes very much in sequence
  2. Easier to implement the logic

 Example: Let us create text file named blk.txt

blk.txt

 A technology that has emerged as the frontrunner for handling Big Data processing is Hadoop.

Create a javascript code as follows and save as blk.js

var fs = require("fs");
var data = fs.readFileSync('blk.txt');
console.log(data.toString());
console.log('Program Ended');

Execute the code. The result is 

A technology that has emerged as the frontrunner for handling Big Data processing is Hadoop.

Program Ended

In this example, program blocks until it reads the file and then only it proceeds to next statement or end the program.

Non Blocking program

  1. Do not execute in sequence
  2. In case a program needs to use any data to be processed, it should be kept within the same block to make it sequential execution.

Example: Use the same input file defined for blocking code example.

Create a javascript code as follows and save as nblk.js

var fs = require("fs");
fs.readFile('blk.txt', function (err,data) {
if (err) return console.error(err);
console.log(data.toString());
});
console.log("Program Ended"); 

Execute the code. The result is

Program Ended

A technology that has emerged as the frontrunner for handling Big Data processing is Hadoop.

This example shows that program doesn’t wait for file reading and prints “Program Ended” first. At the same time, the program without blocking continues to read the file.

  1. Node.js uses Events heavily. Most of Node.js API’s are built on Event driven architecture.

Every action on a computer is an event.

Example: File opening is an event.

Objects in Node.js can fire events like createReadStream object fires when opening or closing a file.

Example: to read a stream of characters in existing file trnk.txt

var fs = require("fs");
var rdstream = fs.createReadStream('trnk.txt');
rdstream.on('open', function(){
console.log("File Opened");
});  

Executing above code you will get result as 

File Opened

You can create, fire and listen to your events using Events module, eventEmitter class.

Events module and eventEmitter class is used to bind events and event-listener.

  1. import events module
  2. create an eventEmitter object
  3. create an eventHandler  

To fire an event use eventEmitter.emit(‘evenName’)

To bind an event handler with an event eventEmitter.on(‘eventName’, event handler)

Example: Refer the following example.

// Import Events module
var events = require('events');
// Create an eventemitter object
var eventEmitter = new events.EventEmitter();
//Create an event handler
var myEventHandler = function () {
console.log('I have completed');
}
// Assign evenhandler to an event
eventEmitter.on('complete', myEventHandler);
 
// Fire the complete event
eventEmitter.emit('complete')

Following is the result after executing the code.

Result: I have completed

For firing an event , use  emit method

For assigning an event, use on method.

The buffers module provides a way of handling streams of binary data.

Nodejs implements Buffer using Buffer class. 

Typically, the movement of data is done with the purpose of processing it, or read it, and make decisions based on it. But there is a minimum and a maximum amount of data a process could take over time. So if the rate at which the data arrives is faster than the rate at which the process consumes the data, the excess data need to wait somewhere for its turn to be processed.

On the other hand, if the process is consuming the data faster than it arrives, the few data that arrive earlier need to wait for a certain amount of data to arrive before being sent out for processing.

That “waiting area” is the buffer! It is a small physical location in your computer, usually in the RAM, where data are temporally gathered, wait, and are eventually sent out for processing during streaming.

Example: An example where you can see buffering in action is when you are trying to read an e-book( of size 500 pages with graphics) in google books. If internet is fast enough, the speed of stream is fast enough to fill up the buffer and send out for further processing, then fill another one and send out for processing, till stream is finished.

If your internet connection is slow, Google books display a loading icon, which means gathering more data or expecting more data to arrive. When the buffer is filled up and processed, google books show the page. While displaying the page, more data continues to arrive and wait in the buffer.

No. Buffer class is part of Global Modules.

- Convert Buffer to JSON

- Reading from Buffers

- Concatenating Buffers

- Compare Buffers

- Copy Buffer

Example:

How to convert binary equivalent of stream xyz to JSON format:

create a javascript file with following code.

var buf = Buffer.from('xyz');
console.log(buf.toJSON());

in the first line buf is the variable and Buffer is the Buffer class. Using toJSON method we can convert code as shown in the result below.

Execute the code : Following is the result

{ type: 'Buffer', data: [ 120, 121, 122 ] }

Duplex: Duplex streams are streams that implement both readable and writable interfaces

Examples:

  1. TCP sockets
  2. zlib streams ( Compression library functionality streams)
  3. cypto streams ( Cryptography functionality streams)

Transform: A type of duplex streams where output is in someway related to the input. Like duplex streams, Transform streams also implement both Readable and Writable interfaces.

Examples:

  1. zlib streams ( Compression library functionality streams)
  2. cypto streams ( Cryptography functionality streams)

Piping is 

- a mechanism where output of one stream is provided as input to another stream 

- normally used to get data from one stream and pass the data to another stream

No limit on piping operations.

Example: Create a text file dataSinput.txt with the following content.

Monday is first day of week

Tuesday is second day of week

Wednesday is third day of week

After executing the following code you can view the contents in the outputfile.

var fs = require("fs"); //import fs module
//creating a readstream to read our inputdatafile dataSinput.txt
var readStream = fs.createReadStream("F://dataSinput.txt");
//creating a writestream(initially empty) which is destination for transferred data 
var writeStream = fs.createWriteStream("F://dataSoutput.txt");
//Use Pipe command to transfer from readstream to writestream. 
//Pipe command takes all data from readstream and pushes it to writestream 
readStream.pipe(writeStream);

Output in dataSoutput.txt can be seen as

Monday is first day of week

Tuesday is second day of week

Wednesday is third day of week

Chaining is

- a mechanism to connect output of one stream to another stream and create a chain of multiple stream operations.

- normally used with piping operations.

Example: Create a text file dataSinput.txt with the following content.

Monday is first day of week

Tuesday is second day of week

Wednesday is third day of week

After executing following code.

var fs = require("fs"); //import fs module
var zlib = require("zlib"); //import zlib module
//creating a readstream to read our inputdatafile dataSinput.txt
var readStream = fs.createReadStream("F://dataSinput.txt");
//create a compressed folder zlib
var czlib = zlib.createGzip();
//creating a writestream(initially empty) which is destination for transferred data 
var writeStream = fs.createWriteStream("F://dataSoutput.txt.gz");
//Use Pipe command to transfer from readstream to gzip. 
//Pipe commands takes all data from readstream and pushes it to compressed writestream file  
readStream.pipe(czlib).pipe(writeStream);
console.log("File Compressed");

You get result as “File Compressed”. And compressed file dataSoutput.txt.gz as output 

Which consists of text file dataSoutput.txt.

Yes.Every method of fs module supports both synchronous and asynchronous forms.

Asynchronous methods take the first parameter of callback function as error and last parameter as completion function.

It is better to use an asynchronous method as it never blocks as program during execution whereas synchronous methods does block the program during execution.

import fs module and declare buffer class

  1. Open the file using fs.open method
  2. Execute the method ftruncate to truncate the opened file. Provide the name of the opened file , length of file after which the file will be truncated.
  3. Read the truncated file after successful truncation using fs.read method and buffer
  4. iclose the file using fs.close method

Example: Create a text file named trnk.txt with Knowledgehut tutorials as text in it

Create a javascript code as follows. Save it as trnkexmpl.js

var fs = require("fs"); //import module
var buf = new Buffer(1024); //define buffer
 
fs.open('trnk.txt', 'r+', function (err,fd) {
if (err) {
return console.error(err);
}
console.log("File opened");
//Truncate the open file)
fs.ftruncate(fd, 12, function(err) {
if (err) {
return console.log(err);
}
console.log("File Truncated")
console.log("Going to read same file") 
fs.read(fd, buf, 0, buf.length, 0 ,function(err, bytes) {
if(err) {
return console.log(err); 
}
//Print only read bytes
if(bytes > 0) {
console.log(buf.slice(0, bytes).toString());
}
 
//Close the opened file
fs.close(fd, function(err){
if (err) {
console.log(err);
}
console.log("File closed successfully");
});
});
});
 
});
 

Execute the code . You get the following result

File opened

File Truncated

Going to read same file

Knowledgehut

File closed successfully

  1. import fs module
  2. delete the file using fs.unlink method and name of file to be deleted as parameter.

Create a text file “demo_file_del.txt” file to be deleted.

var fs = require("fs");  //import fs module
console.log("going to delete demo_file_del.txt file")
fs.unlink('demo_file_del.txt', function(err) { // call unlink method)
if (err) {
return console.err(err);
}
console.log("File deleted successfully")
});

Result:

going to delete demo_file_del.txt file

File deleted successfully

demo_file_del.txt was deleted.

Description

Node.js is a popular open-source server environment which runs on various platforms (Windows, Mac OS, Linux, Unix, etc.). It allows you to build an entire website using one programming language: Javascript. It is one of the most sought-after development tools to learn as the demand for the same has increased and continues to increase. According to Ziprecruiter.com, the average salary of a Node Js Developer is $117,350 per year.

Many reputed companies are hunting for a good web developer and if you’re passionate about becoming a web developer and planning to opt for Node JS as a career building tool, you are already on the right track! Make the best use of your time and be thorough with these Node js interview questions and the best answers. These Node.js interview questions have been designed to get you familiarized with the types of questions that you may encounter in your interviews. Our basic and advanced Node.js interview questions are followed by answers from industry experts so that you can prepare better for your upcoming interviews. These top Node.js interview questions will help to save your time in preparation and will definitely help your interviewer to understand your deep knowledge of Nodejs.

We’ve listed all the frequently asked questions and answers which will help you get a clear understanding of Node.js and they are simple to remember as well. The answers you find here have been prepared by industry experts.

All our interview questions for Node.js are up-to-date with the aim to always keep you updated with the latest interview questions. These Node JS Interview Questions and answers will definitely help you in cracking your interview and follow your dream career as a Node.JS Developer.

Practice well with these interview questions. Be confident, gear up. All the best!

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