Node JS Interview Questions for Freshers

1. What is Node.js?

Node JS is a platform built on Chrome’s JavaScript runtime for easily building fast, scalable network applications and uses an event-driven, non-blocking I/O model that makes it lightweight and efficient, perfect for data-intensive real-time applications that run across distributed devices.

2. Explain CLI in Node.js?

Command-line interfaces (CLIs) built in Node JS allows to automate repetitive tasks while leveraging the vast Node JS ecosystem and package managers like npm and yarn , these can be easily distributed and consumed across multiple platforms.

3. Explain What is a Javascript Engine?

A JavaScript engine is a computer program that executes JavaScript code. In a browser, the JavaScript engine runs in concert with the rendering engine via the Document Object Model. The use of JavaScript engines is not limited to browsers.

4. Explain V8 Engine?

An eight-cylinder engine, the V8, is common in pickup trucks, SUVs and sportscars because these engines create a lot of horsepower, torque and are better suited to tow or haul. It has between four and six litres of displacement, depending on the size of the eight cylinders within.

5. Explain ECMAScript?

ECMAScript is the scripting language standardized by ECMA International in the ECMA-262 specification. ECMAScript is a language specification. Many languages follow and implement the ECMAScript specification, e.g., JavaScript, ActionScript, Nashorn. ECMAScript and languages.

6. What do you mean by Asynchronous API?

Synchronous/asynchronous APIs are application programming interfaces that return data for requests either immediately or at a later time. In the case of asynchronous APIs, the availability of a resource, service or data store may not be immediate.

7. What are the benefits of using Node.js?

Simple to use.
Easy to Learn.
Faster time-to-market.
Scalable.
Single programming language.

8. Is it free to use Node.js?

Node JS is an open-source framework under MIT license.Node.js is a JavaScript runtime built on Chrome’s V8 JavaScript engine.

9. What is REPL in the context of Node?

REPL stands for Read-Eval-Print-Loop which is a quick and easy way to test simple Nodes. Js/JavaScript code. To launch the REPL (Node shell), open command prompt (in Windows) or terminal (in Mac or UNIX/Linux), typenode and can test pretty much any Node.

10. What is Package.json?

A Package.JSON is a JSON file that exists at the root of a JavaScript/Node project. It holds metadata relevant to the project and used for managing the project’s dependencies, scripts, version and a whole lot more.

11. What is an Event Loop?

The event loop is what allows Node.js to perform non-blocking I/O operations — despite the fact that JavaScript is single-threaded — by offloading operations to the system kernel whenever possible. They handle multiple operations executing in the background since most modern kernels are multi-threaded.

12. What is the purpose of Buffer class in Node?

The Buffer class in Node JS is designed to handle raw binary data. Each buffer corresponds to some raw memory allocated outside V8. Buffers act somewhat like arrays of integers, but aren’t resizable and have a whole bunch of methods specifically for binary data.

13. What is Piping in Node?

Piping is a method of transferring data from one stream to other with the help of buffers so that the data transfer process can start as soon as it fills up a buffer. This is a module method to pipe between streams forwarding errors and properly cleaning up and providing a callback when the pipeline is complete.

14. How will you read a file using Node?

Filename holds the name of the file to read or the entire path if stored at other location. Encoding holds the encoding of a file. Its default value is ‘utf8’. callback_functionis a callback function that is called after reading of file.

15. How will you write a file using Node?

There are three ways to write a file:

fs.write(fd, buffer, offset, length, position, callback ) needs to wait for the callback to ensure that the buffer is written to disk. fs.writeFile(filename, data, [encoding], callback) fs.createWriteStream(path, [options] )

16. How will you close a file using Node?

Close() method is used to close the given file descriptor thereby clearing the file that is associated with it. This will allow the file descriptor to be reused for other files. Calling fs.close() on a file descriptor while some other operation is being performed on it may lead to undefined behavior.

17. How will you get information about a file using Node?

Node. js | fs. readFile() Method Filename holds the name of the file to read or the entire path if stored at another location. Encoding holds the encoding of a file. Its default value is ‘utf8’. Callback function is a callback function that is called after reading a file.

18. How will you delete a file using Node?

To delete a file in Node JS use Node FS unlink (path, callback) for asynchronous file operation and unlinkSync (path) for synchronous file operation.

19. Explain What is NPM?

NPM-Node Package Manager is a package manager for the JavaScript programming language maintained by NPM, Inc.js. It consists of a command line client, also called NPM and an online database of public and paid-for private packages, called the NPM registry.

20. Explain Modules in Node Js?

Module in Node JS is a simple or complex functionality organized in single or multiple JavaScript files which can be reused throughout the Node JS application.

21. What are Common JS Modules?

Common JS module is a reusable piece of JavaScript that exports specific objects made available to any dependent code. Unlike AMD, there are typically no function wrappers around such modules.

22. State the specific use of require() in Node Js?

require() is a built-in function with a special purpose used to load modules. Modules are a way to split an application into separate files instead of having all of your application in one file.

23. Explain module.exports in Node Js?

Export is a special object which is included in every JavaScript file in the Node JS application by default. The module is a variable that represents the current module, and export is an object that will be exposed as a module. So, whatever is assigned to module.exports, it will be exposed as a module.

24. Is Node Js Single-threaded?

Node JS is single-threaded similar to JavaScript. So, the JS code is running in a single thread(main thread) in consensus with the event loop and callback queue.

25. What are events?

Much of the Node JS core API is built around an idiomatic asynchronous event-driven architecture in which certain kinds of objects are called “emitters” that emit named events that cause Function objects to be called.

26. Explain event loop in Node Js?
The event loop is what allows Node JS to perform non-blocking I/O operations — despite the fact that JavaScript is single-threaded — by offloading operations to the system kernel whenever possible. Since most modern kernels are multi-threaded, they can handle multiple operations executing in the background.

27. How to create a simple server in Node js that returns Hello World?
To get started with a Node JS web application, initialize the project in the project folder on the terminal too. Open a terminal window and create a new directory called simple_server with mkdir and Initialize the project with npm init.

28. Difference between cluster and child_process modules?
With the cluster module, the creation and sharing of child processes and several parts become easy. In a single thread, the individual instance of node. A developer can access Operating System functionalities by the child_process module, this happens by running any system command inside a child process.
29. How to stop the master process without suspending all of its child processes?
Terminated process is said to be a zombie or defunct until the parent does wait on the child. When a process terminates all of the memory and resources associated with it are deallocated so they can be used by other processes.
30. What does the emitter do and what is the dispatcher?
An Emitter class can be used to raise and handle custom events. It facilitates interaction between objects in Node. A Dispatcher is a service object that is used to ensure that the Event is passed to all relevant Listeners.
31. Since node is a single threaded process, how to make use of all CPUs?
Node JS is one-thread-per-process. If the number of cores is 1, it just simply runs the application as it ran previously. If it has more cores, it detects if the running process is the Master process with the help of a cluster module. It then loops over the number of CPUs of the machine and forks the current process using the cluster. fork() method.
32. List some features of Express JS.

The core features of Express framework:

It can be used to design single-page, multi-page and hybrid web applications.

It allows setting up middleware responding to HTTP Requests.

It defines a routing table which is used to perform different actions based on HTTP method and URL.

33. Write the steps for setting up an Express JS application.

Adding dependencies.

First create a directory for your new application and navigate into it.

Use the npm init command to create a package.json file for the application.

Now install Express in the myapp directory and save it in the dependencies list of the package.json file.

npm install express.

34. What do you mean by Express JS?
Express JS is a back end web application framework for Node JS, released as free and open-source software under the MIT License. It is designed for building web applications and APIs. It has been called the de facto standard server framework for Node.
35. What are the advantages of Passport authentication?
The advantages of Passport authentication are that the user doesn’t have to remember separate usernames and passwords for various Web sites and that the user can maintain his or her profile information in a single location.
36.what is boxing and unboxing?
Boxing is the process of converting a value type to the type object or to any interface type implemented by this value type. Unboxing extracts that value type from the object. Boxing is implicit; unboxing is explicit.
37.List the major built-in objects in ASP.NET?
The built-in objects in ASP.NET are the

application,

session,

context,

request,

response,

server,

trace.

38.What are the different types of cookies in ASP.NET?
There are three types of Cookies – Persist Cookie, Non-Persist Cookie. In this article, we will see how to create a cookie in ASP.NET.
39. What is the file extension of a web service?
Web forms are contained in files with a “.aspx” extension; these files typically contain static HTML markup or component markup. The component markup can include the server-side Web Controls and User Controls that have been defined in the framework or the web page.

40. What are the components of ADO.NET?

ADO.NET components in three categories: disconnected, common, or shared and the . NET data providers. The disconnected components build basic ADO.NET architecture. You can use these components with or without the data providers.

41. What Are The Benefits Of Using Node.js?

Easy to learn.
Keeping things simple.
Faster time-to-market, Scalability.
Battle-tested old hand, MVP development.
Community.

42. Is It Free To Use Node.js?

Node JS is a cross-platform runtime environment for JavaScript, which is free and open-sourced. It is full-stack can be used to develop both the client-side and the server-side of an application.

43. Is Node A Single Threaded Application?

Node JS is a single-threaded application but not purely JavaScript code which implies things that are done asynchronously like network calls, file system tasks, DNS lookup, etc.

44. What Is Repl In Context Of Node?

REPL (Read-Eval-Print-Loop) is a quick and easy way to test simple Node. To launch the REPL (Node shell) – open command prompt (in Windows) or terminal (in Mac or UNIX/Linux) and type node and can now test pretty much any Node.

45. What Is Global Installation Of Dependencies?

The global installation of dependencies in Node JS is putting global packages in a single place in the system exactly where it depends on the setup, regardless of where you run the command to install dependencies.

46. What Is Local Installation Of Dependencies?

Install the dependencies in the local node_modules folder. In global mode (strongi.e, with -g or –global appended to the command), it installs the current package context (i.e, the current working directory) as a global package. By default, npm install will install all modules listed as dependencies in the package.

47. What Is Package.json?

All npm packages contain a file, usually in the project root, called package. json – this file holds various metadata relevant to the project. This file is used to give information to npm that allows it to identify the project as well as handle the project’s dependencies.

48. What Is Callback?

Node JS being an asynchronous platform, doesn’t wait around for things like file I/O to finish – Node Js uses callbacks. A callback is a function called at the completion of a given task preventing any blocking, and allows other code to be run in the meantime.

49. How Node Prevents Blocking Code?

Node JS is a cross-platform JavaScript runtime environment that helps to execute and implement server-side programs. Node is assumed to prevent blocking code by using a single-threaded event loop.

50. What Is an Event Loop?

The event loop allows Node JS to perform non-blocking I/O operations — despite the fact that JavaScript is single-threaded — by offloading operations to the system kernel whenever possible. Since most modern kernels are multi-threaded and can handle multiple operations executing in the background.

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Node JS Interview Questions for Freshers