Node js and Express js Interview Question

1. What is the purpose of Node.js?

Node.js is an open-source and cross-platform runtime environment for executing JavaScript code outside a browser. NodeJS is not a framework and it’s not a programming language. Node.js is used to build back-end services like APIs like Web App or Mobile App. It’s used in production by large companies such as Paypal, Uber, Netflix, Walmart, and so on.

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

Javascript is a high-level programming language that uses the concept of Oops but it is based on prototype inheritance. 1. Javascript is a programming language that is used for writing scripts on the website. NodeJS is a Javascript runtime environment.

3. What is V8?

V8 is the name of the JavaScript engine that powers Google Chrome. It’s the thing that takes our JavaScript and executes it while browsing with Chrome. V8 is the JavaScript engine i.e. it parses and executes JavaScript code.

4. Why we always require modules at the top of a file? Can we require modules inside of functions?

There are several reasion but some of that is given below

1.imagine you had a module that took 30 minutes to load, which is unreasonable, but just imagine. If that module is only needed in one route handler function it might take some time before someone triggers that route and Node.js has to require that module. When this happens the server would effectively be inaccessible for 30 minutes as that module is loaded. If this happens at peak hours several users would be unable to get any access to your server and requests will queue up.

2. If the module you require causes an error and crashes the server you may not know about the error for several days, especially if you use this module in a rarely used route handler. No one wants a call from a client at 4AM telling them the server is down.”

5. What is the purpose of package.json in Node.js?

The package. json file is the heart of any Node project. It records important metadata about a project which is required before publishing to NPM, and also defines functional attributes of a project that npm uses to install dependencies, run scripts, and identify the entry point to our package.

6. What is the main advantage of using Node.js?

Node.js uses an event-driven, non-blocking I/O model that allows it to handle I/O operations more efficiently. By using callbacks, Node.js can continue processing other tasks while waiting for I/O operations to complete. This means that Node.js can handle multiple requests simultaneously without causing any delays.

7. Why are top-level variables not global in modules?

The top level variables in a script are inside a module function and are not global. This is how node. js loads and runs scripts whether specified on the initial command line or loaded with require() . Code run in the REPL is not wrapped in a module function.

8. Why is Node.js so popular these days?

there are several resion some of that

1.Fast development time: One of the benefits of using Node.js for web development is that it can allow for fast development times.

2.Easy to learn: Node.js uses JavaScript, which is a widely-used and well-known programming language. This means that developers who are familiar with JavaScript can easily get started with Node.js, as the syntax and concepts are similar.

3.Large ecosystem: Node.js has a large and active community of developers, which has contributed a wide range of open-source libraries and tools that can be easily integrated into Node.js applications. This means that developers can take advantage of these tools to save time and effort when building their applications.”

9. What is full form of npm?

Node.js | NPM (Node Package Manager) Node.js Global Objects. Node.js Modules.

43. Where can we use node.js?

Node. js is widely used for the back-end of applications, like using Express. js to build the back-end of classic web applications. Also, it is used for server-side programming and non-blocking, event-driven servers like typical websites and backend API services.

10. Is Node.js single-threaded?

Node. js runs JavaScript code in a single thread, which means that your code can only do one task at a time.

11. What is use of node js?

Node. js is single-threaded, we use it primarily for non-blocking, event-driven servers. We can also use Node. js for traditional websites and back-end API services, as it was designed with real-time, push-based architectures in mind.

12. Can variables defined with let keyword be redeclared?

Variable declared by let cannot be redeclared and must be declared before use whereas variables declared with var keyword are hoisted.

13. What is the use of the underscore variable in REPL?

The underscore Variable (_) will give us the result of the last executed command or code. It can be a variable value, function return value, or anything which can return some kind of value, if there is nothing from the evaluation the REPL will default it to undefined.

14. What is error-first callback?

Error-first callback in Node. js is a function that returns an error object whenever any successful data is returned by the function. The first argument is reserved for the error object by the function. This error object is returned by the first argument whenever any error occurs during the execution of the function.

15. What is callback hell?

Callback Hell is essentially nested callbacks stacked below one another forming a pyramid structure. Every callback depends/waits for the previous callback, thereby making a pyramid structure that affects the readability and maintainability of the code

16. Node js Architecture

“Node.js is a JavaScript-based platform that is mainly used to create I/O-intensive web applications such as chat apps, multimedia streaming sites, etc. It is built on Google Chrome’s V8 JavaScript engine. A web application is software that runs on a server and is rendered by a client browser that accesses all of the application’s resources through the internet.

A typical web application consists of the following components:

Client: A client refers to the user who interacts with the server by sending out requests.

Server: The server is in charge of receiving client requests, performing appropriate tasks, and returning results to the clients. It serves as a bridge between the front-end and the stored data, allowing clients to perform operations on the data.

Database: A database is where a web application’s data is stored. Depending on the client’s request, the data can be created, modified, and deleted.”

17. What is the difference between returning a callback and just calling a callback?

callback function is a function that is passed as an argument to another function, which executes the callback function whenever it requires to do so to complete a certain task. Callback function provides a variety of powerful programming techniques. Callback function makes function execution much more dynamic by allowing what kind of action we want to perform using callback.

Returning a callback: In returning a callback, the called function returns a callback instead of executing it immediately. The calling code where the callback is returned can execute the returned callback immediately, pass it to some other function and so on. Lets see an example of a function that returns a callback function.”

19. What is the difference between events and callbacks in Node.js?

When the background task is completed callback function is called. Events: Each action on the computer is called an event. In nodeJS objects can fire events.

20. why does Node.js prefer error-first callback?

Error-First Callback in Node. js is a function which either returns an error object or any successful data returned by the function. The first argument in the function is reserved for the error object. If any error has occurred during the execution of the function, it will be returned by the first argument.

21. How many types of API functions are available in Node.js?

The two types of API functions in Node.js are: Asynchronous, non-blocking functions. Synchronous, blocking functions.

22 What are promises in Node.js?

Promises are used to handle asynchronous operations in JavaScript. Perform operations inside the callback function and if everything went well then call resolve. If desired operations do not go well then call reject.

23. What is event-driven programming in Node.js?

Event-driven programming is used to synchronize the occurrence of multiple events and to make the program as simple as possible. The basic components of an Event-Driven Program are: A callback function ( called an event handler) is called when an event is triggered

24. What are buffers in Node.js?

Buffers are instances of the Buffer class in Node. js. Buffers are designed to handle binary raw data. Buffers allocate raw memory outside the V8 heap.

25. Is Node.js cross-platform?

Yes Node. js is an open-source and cross-platform runtime environment for executing JavaScript code outside a browser

26. What do you understand by the term fork in Node.js?

Fork does not send data automatically, but we can use a global module name process to send data from the child process and in the parent module, using the name of the child the process to send to the child process.

27. Why use Express.js?

28. What is the difference between the global installation of dependencies and local installation of dependencies?

Installing the local dependencies means the module will be available only for a project you installed in the same directory. Global installing dependencies puts the module into your Node and you can able to use this package in your project

29. Why use Express.js over Node.js?

Express.js is a framework based on Node.js which is used for building web-application using approaches and principles of Node.js event-driven architecture.

30. What is the relationship between Node.js and V8?

Node. js is a JavaScript runtime built on top of the V8 JavaScript engine. It allows developers to run JavaScript on the server to build network applications, using JavaScript as the programming language on both the front-end and back-end.

31. What is the purpose of __filename variable?

To get the absolute path of the current file/code. To get the name of the file currently executing.

32. What is the difference between a session and a cookie?

Session save data in encrypted form. Cookies stored on a limited data. Session stored a unlimited data. We can set an expiration date to delete the cookie’s data

33. Explain Express.js Template Engine?

A template engine enables you to use static template files in your application. At runtime, the template engine replaces variables in a template file with actual values, and transforms the template into an HTML file sent to the client. This approach makes it easier to design an HTML page.

34. What function as arguments are available to ExpressJS route handlers?

It is the response object. Req – It is the request object. Next (optional) – This argument is used for passing the management to any of the above-given route handlers.

35. What is error first callback function?

36. What functions are arguments available to ExpressJS route handlers?

The arguments that are available in the route handler function of Express JS are given below:

Res – It is the response object.

Req – It is the request object.

Next (optional) – This argument is used for passing the management to any of the above-given route handlers.”

37. What is scaffolding in Express.js?

Scaffolding is creating the skeleton structure of application. It allows users to create own public directories, routes, views etc. Once the structure for app is built, user can start building it. Express is the open source web development framework for Node

38. What do you understand by the term I/O?

Node. js uses an event-driven, non-blocking I/O model. 2. The I/O (Input/Output) model refers not just to the input/output operations but also to anything ranging from writing/reading files on your local system to making an API request to read/write data to a remote system to routing the requests.

39. What are some popular frameworks or libraries used with Node.js?

“Some popular node js library is

Express ,Socket.io,Async.Js, Ethers.js, mongoose.

40. What is the meaning of HTTP status code 504?

504 Gateway Timeout.

41. How can you listen on port 80 with Node?

“we need to import ‘http’ module and then call its createServer method to create a server. The server is set to listen on the specified port and hostname. When the server is ready, the callback function is called, in this case informing us that the server is running. const server = http.

http is the default network port used to send and receive unencrypted web pages”

42. What is the shortcut for killing a process in Node.js?

Method 1: Using ctrl+C key: When running a program of NodeJS in the console, you can close it with ctrl+C directly from the console with changing the code shown below: Method 2: Using process. exit() Function: This function tells Node. js to end the process which is running at the same time with an exit code.

43. Which function is used to fire an event?

Every event is named an event in nodeJS. We can trigger an event by emit(event, [arg1], [arg2], […]) function. We can pass an arbitrary set of arguments to the listener functions.

44. Define Express.js and explain its purpose.

Express.js is a small framework that works on top of Node.js web server functionality to simplify its APIs and add helpful new features. It makes it easier to organize your application’s functionality with middleware and routing. It adds helpful utilities to Node.js HTTP objects and facilitates the rendering of dynamic HTTP objects.

a .Develops Node.js web applications quickly and easily.

b. It’s simple to set up and personalise.

c .Allows you to define application routes using HTTP methods and URLs.

d. Includes a number of middleware modules that can be used to execute additional requests and responses activities.

e .Simple to interface with a variety of template engines, including Jade, Vash, and EJS.

f .Allows you to specify a middleware for handling errors.”

45. What is the significance of using Express.js in web development?

express is a small framework that sits on top of Node. js’s web server functionality to simplify its APIs and add helpful new features. It makes it easier to organize your application’s functionality with middle ware and routing. It adds helpful utilities to Node.

46. How can CORS be enabled in an Express.js application?

The easiest way to get CORS working in Express is by using the cors npm module. That’s it. CORS is now enabled. The Access-Control-Allow-Origin header determines which origins are allowed to access server resources over CORS (the * wildcard allows access from any origin)

47. Compare Express.js and Node.js in terms of their roles and functionalities.

refer this link :

48. What parameters are available in an Express.js route handler function?

The parameters of router.param() are a name and function. Where the name is the actual name of the parameter and the function is the callback function. Basically, the router.param() function triggers the callback function whenever the user routes to the parameter. This callback function will be called only a single time in the request-response cycle, even if the user routes to the parameter multiple times.

Syntax: router.param(name, function).

49. Describe how error handling is implemented in Express.js, including an example.

Express has built-in error handling middleware, such as the app. use(function(err, req, res, next) {}) function, which can be used to handle errors that are thrown or passed to the next() function. You can also create your own error-handling middleware functions to handle specific errors in your application.you can use also try catch and promies to handle the error

50. Define middleware in the context of Express.js and discuss the different types available.

Middleware in Express. js is a function that is accessible to the request, response objects and the next middleware function. It can execute any code, terminate the request-response cycle, make needed changes in req and res objects, and detect errors.

51. How does Express.js handle middleware?

Express middleware refers to a set of functions that execute during the processing of HTTP requests received by an Express application. Middleware functions access the HTTP request and response objects. They either terminate the HTTP request or forward it for further processing to another middleware function.

52. What are the two arguments that async.queue takes?

A queue object based on an asynchronous function can be created which is passed as a worker. Task: Here, it takes two parameters, first — the task to be performed and second — the callback function.

53. How can you handle asynchronous operations in Node.js?

Await function can be used inside the asynchronous function to wait for the promise. This forces the code to wait until the promise returns a result. Use async inside your Node. js project using require() method.

54. When are we required to use a cluster module in Node.js?

Node. js runs single threaded programming, which is very memory efficient, but to take advantage of computers multi-core systems, the Cluster module allows you to easily create child processes that each runs on their own single thread, to handle the load.

55. What’s Punycode in Node.js?

Punycode is a character encoding scheme defined by RFC 3492 that is primarily intended for use in Internationalized Domain Names. Because host names in URLs are limited to ASCII characters only, Domain Names that contain non-ASCII characters must be converted into ASCII using the Punycode scheme

56. Explain the use of passport module in Node.js

The passport module is used for adding authentication features to our website or web app. It implements authentication measure which helps to perform sign-in operations.

57. What is the use of url module in Node.js?

In Node.js url module is used to split the URL of the website into parts so that it becomes readable and can be used in the different parts of the application. The parse() method is used with the url module to separate the URL of the website into parts.

58. What is REST API?

Representational State Transfer (REST) is an architectural style that defines a set of constraints to be used for creating web services. REST API is a way of accessing web services in a simple and flexible way without having any processing. It works after the request is sent from the client to the server in the form of a web URL as HTTP GET or POST or PUT or DELETE request. After that, a response comes back from the server in the form of a resource which can be anything like HTML, XML, Image, or JSON. But now JSON is the most popular format being used in Web Services.

59. Explain what dynamic routing is in Express.js

dynamic routes allows us to pass parameters and process based on them. Here is an example of a dynamic route − var express = require(‘express’); var app = express(); app. get(‘/:id’, function(req, res){ res.send(user)})

60. What are the different kinds of HTTP requests?

“The most commonly used HTTP requests are:

GET: This request is used to read/retrieve data from a web server. GET returns an HTTP status code of 200 (OK) if the data is successfully retrieved from the server.

PUT: This request is used to modify the data on the server. It replaces the entire content at a particular location with data that is passed in the body payload. If there are no resources that match the request, it will generate one.

POST: This request is used to send data (file, form data, etc.) to the server. On successful creation, it returns an HTTP status code of 201.

DELETE: This request is used to delete the data on the server at a specified location.

61. Why should you separate Express ‘app’ and ‘server’?

separating the app. js and server. js files in an Express. js application can improve code organization, maintainability, and testability.

62. Explain the engine Google uses for Node.js

The engine used by Google for Node.js is V8. It is one the fastest engine as it is written in C++. It provides a runtime environment for the execution of JavaScript code. The best part is that the JavaScript engine is completely independent of the browser in which it runs. It has a huge community and is highly portable.

63. How many layers are there in Node.js application architecture?

With the popular Node. js framework Express. js, developers can follow the “separation of concerns” principle during development. By dividing the codebase into three categories – business logic, database, and API routes, which fall into three different layers, service layer, controller layer, and data access layer.

64. How does Express.js handle file uploads?

To handle file uploads in Express. js, you can use middleware such as Multer, a Node. js middleware used for handling multipart/form-data, which is mainly used for file uploads.

65. What is the purpose of the next() function in Express.js?

The next function is a function in the Express router which, when invoked, executes the middleware succeeding the current middleware. Middleware functions can perform the following tasks: Execute any code. Make changes to the request and the response objects.

66. What are streams in Node.js?

Streams are a type of data-handling method 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. The stream module provides an API for implementing the stream interface. Examples of the stream object in Node.js can be a request to an HTTP server and process.stdout are both stream instances.”

67. How does Node.js handle blocking and non-blocking operations?

“Blocking: It refers to the blocking of further operation until the current operation finishes. Blocking methods are executed synchronously. Synchronously means that the program is executed line by line. The program waits until the called function or the operation returns.

Non-Blocking: It refers to the program that does not block the execution of further operations. Non-Blocking methods are executed asynchronously. Asynchronously means that the program may not necessarily execute line by line. The program calls the function and move to the next operation and does not wait for it to return.”

68. What are the differences between spawn, fork, and exec in Node.js?

Spawn

require(‘child_process’).spawn() starts sending back data from the child process in a stream as soon as the child process starts executing. When you run this command, it send a system command that will run on its own process rather than executing code within your node process. In this no new V8 instance will be created and only one copy of the node module will be active on the processor. It is used when you want the child process to return large amount of data to Node.

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

Fork

require(‘child_process’).fork() is a special instance of spawn thats runs a new instance of the V8 engine. Which actually means you are creating multiple workers running on the same Node code base for different taskyNode

s = require('fs');
process = require('child_process');
var ls = process.fork('YourJs.js');
ls.stdout.on('data', function(data)) {
console.log('stdout: ' + data);
});

require(‘child_process’).exec() returns a buffer from the child process. The default buffer size is 200k. It is asynchronous, but it waits for the child process to end and tries to return all the buffered data at once. If your return data from the child process is greater than 200k then you will get maxBuffer exceeded.

fs = require('fs');
process = require('child_process');
var ls = process.exec('node YourJs.js', function (error, stdout, stderr) {
      if(error)
console.log(error.code);
});

69. What is the role of the event loop in Node.js?

An event loop is an endless loop, which waits for tasks, executes them, and then sleeps until it receives more tasks. The event loop executes tasks from the event queue only when the call stack is empty i.e. there is no ongoing task. The event loop allows us to use callbacks and promises

70. How can you scale a Node.js application to handle high traffic loads?

js application can be scaled horizontally using multiple servers as long as the application is running as an independent process. A load balancer can be introduced to handle scaling across servers, where the load balancer will distribute the requests among servers depending on the load.

71. How to obtain the IP address of the user in Node.js?

“The Domain Name System is a hierarchical and decentralized naming system for computers etc that are connected to the Internet. To find the IP address of the user in Node.js we use dns.lookup() method of dns module.

dns.lookup() function:

dns.lookup(hostname[, options], callback)

Parameters:

Hostname: It consists website link which is valid or active.

Option: Default value is 0. It can be 0, 4 or 6 which indicates IPv4 and IPv6 addresses.

Callback: This function has user’s IP address and family(i.e. IPv4 and IPv6) and error.”

72. How can you handle memory leaks in Node.js?

A quick way to fix Node. js memory leaks in the short term is to restart the app. Make sure to do this first and then dedicate the time to seek out the root cause of the memory leak.

73. What do you understand by an EventEmitter in Node.js?

“EventEmitter is a class in node.js that is responsible for handling the events created using the ‘events’ module in node.js. Events are created to make custom operations while a set of operations is performed. EventEmitter can return two properties namely newListener if we want to create a new event listener and removeListener when we want to remove existing event listeners. Both of these mentioned properties emit an event whenever called to perform the operation.

In order to perform operations on EventEmitter, we need to create a reference using the ‘events’ module and then we need to initialize an instance of the EventEmitter so that we can use it further.

Syntax:

//Creating a constant reference of EventEmitter
const EventEmittter = require('events');
// Initializing instance of EventEmitter
const emitter = new EventEmitter();"

74. How would you render plain HTML in Express.js?

“Express Js is the web application framework based on Node.js web server functionality that helps us to create the application endpoints that respond based on the HTTP request (POST, GET, etc) method and the requested route. The res.sendFile() method of the express.js module is used to render a particular HTML file that is present in the local machine.

Syntax:

res.sendFile(path,[options],[fn])”

75. How to generate a token using JWT in Express app?

“A JSON web token(JWT) is JSON Object which is used to securely transfer information over the web(between two parties). It is generally used for authentication systems and can also be used for information exchange.

This is used to transfer data with encryption over the internet also these tokens can be more secured by using an additional signature. These token consists of header JSON and payload JSON along with the optional signature, The each of three remains concatenated with the JSON Web Token.

Step 1: Initialize server & Install JWT Package.

npm init

npm install jsonwebtoken

Step 2: Create Route for Tokens

Explanation:-

We have imported the express, mongoose, and jsonwebtoken in the first line, and also the User model because that would be necessary to interact with the database. In the next line, we have called the express method which returns an app with which we can configure our server. We are using express.json middleware in the starting because so that server can identify the incoming requests as JSON objects.

After then we have created two routes one for login and the other for signup.

Inside the Login route, we have extracted the email and password from the request body and then searched for the user in the database if that is found we are proceeding to check whether the provided password matches with an actual password or not.

Inside the signup route, we have extracted details like name, email, and password to register users in the database, with the save method provided by the mongoose.

76. Name some of the unique Express.js features.

“Faster Server side development. Express. …

Middleware. Middleware is a part of the program that has access to the database, client request, and the other middlewares. …

Routing. …

Templating. …

Debugging.”

77. How to upload a file using formidable in Express.js?

“A formidable module is used for parsing form data, especially file uploads. It is easy to use and integrate into your project for handling incoming form data and file uploads.

npm install formidable

Installation of the formidable module:

After that, you can just create a folder and add a file

NOTE: ‘uploads’ is the folder where your files will be uploaded. beter understanding refer to this article

78. How to Upload File using formidable module in Node.js ?

A formidable module is used for parsing form data, especially file uploads. It is easy to use and integrate into your project for handling incoming form data and file uploads.

npm install formidable

Installation of the formidable module:

After that, you can just create a folder and add a file

NOTE: ‘uploads’ is the folder where your files will be uploaded. beter understanding refer to this article

https://www.geeksforgeeks.org/how-to-upload-file-using-formidable-module-in-node-js

79. How to make the cookie more secure for the client through Express JS?

“Cookies are small data that are stored on a client side and sent to the client along with server requests. Cookies have various functionality, they can be used for maintaining sessions and adding user-specific features in your web app. For this, we will use cookie-parser module of npm which provides middleware for parsing of cookies.

80. First set your directory of the command prompt to root folder of the project and run the following command:

npm init

This will ask you details about your app and finally will create a package.json file.

After that run the following command and it will install the required module and add them in your package.json file

npm install express cookie-parser –save

after that you use this code

let express = require('express');
//setup express app
let app = express()
//basic route for homepage
app.get('/', (req, res)=>{
res.send('welcome to express app');
});
//server listens to port 3000
app.listen(3000, (err)=>{
if(err)
throw err;
console.log('listening on port 3000');});

83. What are the timing features of Node.js?

“setTimeout/clearTimeout – This is used to implement delays in code execution.

setInterval/clearInterval – This is used to run a code block multiple times.”

84. Explain what is Reactor Pattern in Node.js?

The Reactor Pattern is a design pattern that is used to simplify the process of building scalable network servers in Node. js. It is based on the idea of a “reactor,” which is an event loop that listens for incoming requests and delegates them to the appropriate handler function.

85. What is LTS releases of Node.js why should you care?

LTS releases, also known as “stable” releases, are versions of Node. js that are designated for long-term support. This means that they are more stable and reliable than standard releases, which are meant for testing and experimentation.23

86. What is the difference between process.nextTick() and setImmediate() ?

setImmediate adds callbacks to the event queue that are executed during the check phase, whereas process. nextTick executes callbacks immediately after the current phase.

“Rewrite the code sample without try/catch block

consider code is :Node

async function check(req, res) {
try {
const a = await someOtherFunction();
const b = await somethingElseFunction();
res.send(""result"")
} catch (error) {
res.send(error.stack);
}
}	
async function check(req, res).then(data){
if(data) {
const a = await someOtherFunction();
const b = await somethingElseFunction();
res.send(""result"")
} 
}.catch (error) {
res.send(error.stack);
}

87. How does concurrency work i node.js

Concurrency is an essential feature of Node. js that enables it to handle large numbers of I/O operations simultaneously, without blocking the execution thread. This concurrency model allows Node. js to handle many requests concurrently, resulting in improved application performance.

88. Are you familiar with child_process module?

The child_process module enables us to access Operating System functionalities by running any system command inside a, well, child process. We can control that child process input stream, and listen to its output stream.

89. What is the difference between spwan exec and fork?

90. Is there any reason to use child_process for intensive i/o work?

Usually, Node. js allows single-threaded, non-blocking performance but running a single thread in a CPU cannot handle increasing workload hence the child_process module can be used to spawn child processes. The child processes communicate with each other using a built-in messaging system.

91. What are cyclic module dependencies in Node?

That is – since the circular dependency means that other code receives an incomplete module object, the proposed solution is to ensure the incomplete module will have the necessary objects in it. A circular dependency between Node. js modules occurs when the modules require() each other

92. What is the role of async_hooks module in nodejs?

Async_hooks module is used because it provides an API to register callbacks tracking the lifetime of asynchronous resources created inside a Node. js application. Features: You can capture any asynchronous activity in a Node.

93. Can node js perform cryptographic functions?

Yes, Node.js can perform cryptographic functions. Node.js has a built-in “crypto” module that provides various cryptographic functionalities, such as hashing, encryption, and decryption.

94. How can we perform asynchronous network API in Node JS?

Asynchronous tasks that should occur in an event loop in Node.js include I/O operations, timers, and callback functions. By performing these tasks asynchronously, Node.js can handle a large number of concurrent requests without blocking the event loop.

95. How can we take advantage of multi-core system in Nodejs as nodejs works on single thread?

NodeJS receives multiple client requests and places them into EventQueue. NodeJS is built with the concept of event-driven architecture. NodeJS has its own EventLoop which is an infinite loop that receives requests and processes them

96. What’s the difference between operational and programmer errors?

Operational errors are a natural part of an application, and programmer errors are bugs caused by developers.

97. Could we run an external process with Node.js?

The child_process module provides us with the capability to run external processes in Node. js With the help of the child process module, we may use any system command as a “child process” to access Operating System features.

98. What is Piping in Node?

Piping in NodeJS is the process by which byte data from one stream is sent to another stream. What are streams? Streams in NodeJS are a sequence of bytes. When a program processes some data it needs to read all the data into memory and then process it and write out the data back into some location.

Name some of the events fired by streams.

“These following event fire by the event

data − This event is fired when there is data is available to read.

end − This event is fired when there is no more data to read.

error − This event is fired when there is any error receiving or writing data.

finish − This event is fired when all the data has been flushed to underlying system.”

99. What’s a stub? Name a use case.

Stubs are functions/programs that simulate the behaviors of components/modules. Stubs provide canned answers to function calls made during test cases. An example can be writing a file, without actually doing so.

100. How to stop the master process without suspending all of its child processes?

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.

101. How can you use a Pug template engine inside Express?

Install PUG in our Node application as a dependency:

he pug must simply be added to the app.js file as the new view engine.

make view file inside src which contain html file after that run like this

Add the following code:

app.set(“”view engine””, “”pug””);

app.set(“”views””, “”./src.views””);

In other words, we are telling Express where to locate the templates and that you want to create dynamic content using the Pug templating engine. Save all of the data, then utilize the servers:

npm start

102 How can you deploy Node.js applications?

“Task 1 – Git clone the application repository

Task 2 – NPM install dependencies

Task 3 – Configure a program for Supervisor

Task 4 – Supervisor – Reread & Update program configuration

Task 5 – Symlink release

Task 6 – Supervisor – Restart all services

these are the process of deploy the node application”

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