Top 100 Node.js Interview Questions and Answers

An open-source, cross-platform execution system for JavaScript is Node.js. It is a well-liked instrument for almost any job type! The heart of Google Chrome, the V8 JavaScript engine, is operated by Node.js outside of the browser. Node.js can be very performant because of this. Without starting a new thread for each request, a Node.js application works in a single process. Blocking behavior in Node.js libraries is the exception rather than the rule because libraries in Node.js are typically built using non-blocking paradigms and because Node.js offers a collection of asynchronous I/O primitives in its standard library that prohibit JavaScript code from blocking. Instead of stopping the process and squandering CPU time waiting for an I/O action, such as reading from the network or entering a database or filesystem, Node.js will continue its work once the answer has been received. This eliminates the load of handling thread concurrency, which could be a significant cause of bugs, and enables Node.js to manage thousands of concurrent connections with a single server. Node.js has a distinct benefit because it allows the millions of frontend writers who write JavaScript for the browser to write both server-side and client-side code without having to switch to a new language.

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Top 100 Node.js Interview Questions and Answers 2023

1. Describe Node.js.

JavaScript code can be executed outside of an online browser using the open-source, cross-platform Node.js runtime environment.

2. What is Node.js used for?

Building robust network apps requires the use of Node.js.

3. Describe NPM.

The Node.js package manager is called npm. It offers a method for managing and distributing the tools (libraries, frameworks) required to create a Node.js application.

4. What in Node.js is an event?

A signal that a computer can watch for and respond to is what Node.js refers to as an event.

5. What does a Node.js return method do?

In Node.js, a callback function is a function that receives input from another function and is called once that function has finished its job.

6. What distinguishes synchronous programming from asynchronous programming?

Tasks are carried out sequentially, one at a time, in synchronous computing. Asynchronous computing allows activities to run concurrently without waiting for one another.

7. In Node.js, what is a promise?

In Node.js, a promise is a tool for managing deferred tasks. It can be used to prevent callback hell and symbolizes the ultimate success (or failure) of an asynchronous action.

8. In Node.js, what’s the distinction between require and import?

In Node.js, importing a module is done with a method called require, whereas in ES6, importing a module is done with a declaration called import.

9. What does Node.js middleware do?

In Node.js, middleware refers to a function or group of functions that the Express.js transport layer calls before invoking the actual request manager.

10. In Node.js, what is a stream?

In Node.js, a stream is a constant data movement. Instead of putting the complete data set into memory, it enables you to access or send data in small segments.

11. What is Express.js, exactly?

A well-liked online application platform for Node.js is called Express.js. It offers a selection of tools for creating web apps, including middleware, routing, and scripting.

12. What does the Node.js cluster module serve?

By allowing Node.js apps to employ all available CPU cores, the Node.js cluster module enhances speed.

13. What distinguishes the HTTP PUT and POST methods?

Existing resources are updated using the PUT method, while new resources are created using the POST method.

14. What distinguishes the HTTP GET and POST methods?

While the POST method is used to send data for server processing, the GET method is used to obtain resources.

15. How do REST and SOAP vary from one another?

While SOAP is a protocol used in the application of web services, REST is a lightweight design approach for creating distributed systems.

16. What does a Node.js web connection do?

The mechanism for two-way contact between a client and a server in Node.js is called a web socket.

17. What is Express software, exactly?

Before calling the final request handler, Express middleware is a function or collection of methods that are executed by the Express.js routing layer.

18. What advantages does using Node.js offer?

Utilizing Node.js has advantages such as shorter development times, enhanced flexibility, and improved speed.

19. In Node.js, what function does the package.json file serve?

A Node.js application’s components, scripts, and information are defined in the package.json file.

20. What function does the Node.js node_modules subdirectory serve?

All of a Node.js application’s components (packages) are kept in the node_modules subdirectory.

21. What is a return purgatory, exactly?

When multiple callbacks are used in an asynchronous action, it can lead to callback purgatory, which produces unreadable and difficult-to-maintain code.

22. What distinguishes Express.js’s res.send() and res.json() functions?

In contrast to res.json(), which transmits the HTTP answer as JSON, res.send() sends the HTTP response as a string.

23. What is the Node.js REPL?

The interactive command-line utility Node.js REPL (Read-Eval-Print Loop) enables programmers to run Node.js code samples and see the results right away.

24. How do I build and launch a Node.js application?

You must install Node.js, make a project subdirectory, generate a package.json file, install dependencies, write your code, and then execute it using the node program to build and operate a Node.js application.

25. What in Node.js is PM2?

A process scheduler for Node.js is called PM2. It provides automated recovery and lets you control and watch over your Node.js apps.

26. How do Node.js’s EventEmitter and Streams vary from one another?

While Streams are used to continuously receive and write data, EventEmitter is used to transmit information between various program components.

27. How should Node.js failures be handled?

Error-first callbacks, toss and catch blocks, and exceptions can all be used in Node.js to manage problems.

28. Describe NPM.

As a result of node js having its package manager, known as NPM, Javascript can work in a runtime context.

29. What does Node.js’ CLI mean?

The 900000 packages available for Node.js linked to a vast network are one of the key factors in its growing popularity. You can use the command-line interface, or CLI, to automate your duties by utilizing this sizable environment. Additionally, you can distinguish your suggested programs within the community by writing CLI.

30. What language is Node Js developed in?

The interoperability of Node.js with three different languages kinds Javascript Java C C++

31. Who is the Node Js author?

Node.js was created by Ryan Dahl, and the javascript framework first appeared on the scene almost 13 years ago. Node was initially backed by Linux and Mac OS X, but Joyent subsequently became a sponsor.

32. Describe the Javascript Engine.

You can think of a javascript engine as computer software that executes java code because it is used to process the java code in the browser. It was initially only used for interpretation, but as time went on, it progressed and developed. The person who creates the javascript engine for all platforms typically works alone.

33. Describe the V8 engine.

When Google Chrome first debuted in 2008, Chrome also unveiled its V8 engine initiative at the same time. It is a network that is open-source and can be created in C++.

34. ECMAScript: What Is It?

Ecmascript, which was created and defined by Esma Internationals, made its debut in 1997. Evmascriot is a computer language that also gave rise to several other scripts, including the most widely used javascript and ActionScript.

35. What do Node Js modules do?

Node.js uses modulus, a collection of instructions, to carry out operations like addition, subtraction, multiplication, and division. In summary, modulus can be used to perform arithmetic in js.

36. What prevalent Modules are there?

The numerous common moduli in js include addition, subtraction, multiplication, division, exponentials, increment, and decrements.

37. What does Node Js require() use?

Two major managing components run Modulus. The program “Require” is the element. They are both accessible on a worldwide scale.

38. What does the Node Js module export?

Every Node.js file contains a default program called a module. exports.

39. Node Js is single-threaded, correct?

Node Js is single-threaded but also non-blocking, which means that while using node js, a variety of tasks, such as callbacks, are completed in the process using various threads or multiple threads.

40. Which incidents are they?

The incident can be attributed to the actions taken. For instance, when you access a file or close a file, an event has occurred. With the “Events” default module in Node js, you can perform a variety of tasks like create, fire, monitor, and more.

41. What does Node Js’ event loop do?

The event loop is used by Node Js to carry out non-blocking tasks.

42. How do I build a straightforward Node JS server that responds Hello World?

For this procedure, the following actions must be taken:

The necessary package should be imported.
Utilize HTTP.createServer to create the server.().
Examine the request and watch for an answer

43. How can the main process be terminated without also suspending all of its child processes?

The master process can be stopped using the process control tool Upstart. Typically, when the master process is terminated or halted, the child process keeps running.

44. What distinguishes the child_process and cluster modules?

A cluster is created when a single master program is operating on two or more nodes simultaneously.

A child process is merely a new script that is started on the system; it is very similar to the cluster but is written in a different language.

45. What are an emitter and a scheduler, respectively?

A transmitter is a device that allows two nodes to communicate with one another. When a program’s scheduler’s task is finished, dispatched enters the picture and moves the task to the intended status.

46. How can all CPUs be used since the node is a single-threaded process?

Despite being single-threaded, the node js is a topology, which implies that there is communication between two nodes, as the node name itself indicates. All CPUs are used for this transmission between the two nodes.

47. Mention the different npm module types that are accessible and frequently used.

Some of the npm modules include Express, Connect, socket.io and SockeJS, Pug, MongoDB and Mongojs, Redis, Lodash, Forever, Bluebird, and Moment.

48. What characteristics does a container have.json

Name, version, summary, the home page, author, contributors, list of dependencies, repository type, URL, the primary entry point of the package, and keywords.

49. Describe REPL.

Read, Eval, Print, Loop, or REPL.

It is a setting where instructions can be entered to carry out REPL operations. Every one of the duties has a corresponding operation.

50. What types of apps can be created with Node.JS?

The best Node.JS apps are DIRT, JSON, I/O bound, and single page.

51. What NodeJS version is currently in use?

Currently, Node is running version 16.3.0.

52. The foundation of NodeJS. False or True.

False. It is not a system, but a runtime or an environment.

53. What does a Node JS error-first response do?

We must confirm that the code was executed without errors if we want to ensure that it is functioning properly. Error-first callbacks are used in this situation, which transmits the error first and then any relevant data after that.

54. What is the cluster, exactly?

Cluster is a method for managing the burden of thread execution on multi-core systems.

55. Why is a node a single-threaded program?

Single-thread actions are more effective at improving performance than multi-threaded operations.

56. What function does the Nodemailer tool serve?

It must be loaded using npm because it is not among the pre-installed modules.

57. What do NodeJS event injectors do?

To keep the core API’s asynchronous processing in place, objects in NodeJS will need to initiate events. These things are referred to as event emitters because they release events.

58. What are the attendees of events?

To keep the threads running asynchronously, event emitters must wait for events that they emit. Listeners are those things that pay attention to events that are emitted.

59. What does “event-driven programming” mean to you?

An approach called event-driven programming strongly relies on events to start all sorts of different processes. An event can be anything, such as a keystroke or mouse touch.

60. What does an exam pyramid mean to you?

A test pyramid is essentially a diagram that shows the ratio of the number of unit tests, integration tests, and end-to-end tests that must be created for the project to be developed successfully.

61. What does a Node.js error-first function do?

In Node.js, mistakes and data are passed using error-first callbacks. These functions require an error object as their first parameter, with the other parameters denoting the related data.

62. What does “event-driven programming” mean to you?

Describe the function of the module. exports.In Node.js, a module is used to group all the related pieces of code into a unique unit that can be read by moving all related functions into a single file.

63. What does the Node.js Reactor Pattern mean to you?

In Node.js, the Reactor Pattern is essentially a notion of non-blocking I/O processes. Each I/O operation has a handler provided by this pattern, and as soon as an I/O request is produced, it is sent to a demultiplexer.

64. What do Node.js LTS versions consist of?

The Node.js LTS version, which stands for Long Term Support, gets all important bug fixes in addition to security updates and performance enhancements.

65. What exactly do you mean by “callback hell”?

Callback The Pyramid of Doom is another name for Hell. It is a pattern brought on by densely nested callbacks that are cumbersome and difficult to comprehend.

66. Describe libuv.

The multi-platform Node.js module Libuv is primarily used for asynchronous I/O. Although it was initially created for Node.js, it is now frequently used with other platforms such as Luvit, pyuv, Julia, etc. According to the platform, Libuv is essentially an abstraction of libev or IOCP that offers users an API built on libev.

67. What does Node.js’ middleware notion entail?

Middleware is typically a method that accepts the Request and Response objects. In other words, these functions have access to different requests throughout the request-response cycle of a program.

68. What does ESLint mean to you?

ESLint is an open-source project that Nicholas C. Zakas created in 2013 to offer linting functionality for JavaScript via a module.

69. Why does Google use the V8 engine for Node.js?

V8 is a Chrome runtime engine that Google employs to translate JavaScript code into native machine code.

70. Describe how the control flow mechanism operates.

The code that is run in between delayed function calls in Node.js is known as the control flow function.

71. What are the differences between Node.js’s seed() and fork() methods?

The spawn() function in Node.js is used to start a new process with the given collection of commands. A new instance of the V8 engine is executed by the fork() unique spawn() function in Node.js.

72. What does Node.js mean when it refers to global objects?

Globals in Node.js are objects that have a universal scope and are present in all application modules.

73. Describe the Node.js stub idea.

Stubs are essentially the applications or functions used in Node.js to stimulate module or component activity.

74. What does the ExpressJS package’s purpose?

A framework called Express.js, which is based on Node.js, makes it easier to handle the data flow between servers and routes in server-side applications.

75. What does a buffer class in Node.js do?

In Node.js, the buffer class is used to store the raw data in a way akin to an array of integers. However, it relates to a raw memory allotment outside of the V8 heap.

76. How are the child processes handled by Node.js?

Node.js typically runs as a single thread and doesn’t disclose any child threads or thread management techniques.

77. Explain the different kinds of streams available in Node.js.

Similar to arrays and characters, streams are collections of data in Node.js. They are tools that let you continuously receive data from a source or write data to a destination.

78. What purpose does NODE_ENV serve?

Node.js encourages the practice of using the NODE_ENV variable to identify projects that are in the production stage.

79. What does Node.js’s Punycode notion mean?

Punycode is an encoding syntax used in Node.js to translate a line of Unicode (UTF-8) characters into a simple ASCII string of characters.

80. Is there a debugger provided by Node.js?

A straightforward TCP-based interface and an integrated debugging client are provided by Node.js. You can use the debug argument listed below along with the name of the JavaScript file you want to debug to examine it.

81. Does Node.js enable cryptography?

Through the use of the Crypto module, Node.js does indeed enable cryptography. This module offers several cryptographic features, including cipher, decipher, sign, and verify functions, as well as several wrappers for the HMAC hash function used by open SSL.

82. What does a Node.js buffer class do?

Similar to a collection of integers, a buffer class stores raw data, but it equates to a raw memory allocation outside the V8 heap. These have several methods designed especially for binary data and are not resizable. A buffer class is used because binary data cannot be handled by pure JavaScript.

83. What does Node.js pipeline mean?

The mechanism known as piping in Node.js connects the output of one stream to another or numerous streams.

84. What are you aware of regarding node.js streams?

Streams in Node.js are examples of EventEmitter. They can be used to handle and manipulate streaming big files (like videos and mp3) over the network when working with streaming data in Node.js.

85. Describe middleware.

In the request-response cycle of the application, a middleware function has access to the answer object, the request object, and the following middleware function.

86. What are the Node.js termination codes?

Node.js’ exit codes indicate the cause of code termination.

87. Describe WASI.

The WebAssembly System Interface is known as WASI. It is a collection of capability-focused APIs designed to unify the execution of WebAssembly modules in sandboxes outside of browsers.

88. Tell us about event-driven content.

Events are programs that are dependent on how users engage with a graphical user interface, such as clicking a submit button, choosing an option from a radio button, typing text into a text field, or uploading an image file.

89. Explain the Node.js Event Loop.

Event Loop is a mechanism that enables Node.js to continue uninterruptedly conducting I/O operations to the system kernel.

90. Describe the Node.js error first response.

Error-first Node.js’s callback function is used to send data and errors. The callback is an asynchronous procedure that is made after the Ajax request has been fulfilled.

91. How does Node.js’ DNS function work?

Functionalities like Domain Name System (DNS) search and operating system name resolution uses the DNS module.

92. How is Node.js using assert?

Function assertion uses the Node.js Assert components. The assert method checks invariants and outputs nothing if the condition is met; otherwise, the console displays an assertion error.

93. Use of the URL module in Node.js

A URL is made up of several components, including a protocol, address and port, file path, and filename. Node.js’s URL module assists in breaking up web addresses (URLs) into digestible chunks for users.

94. Describe the Node.js package’s package.json file.

The JSON file json is located in the Node.js root directory and includes information about projects such as their description, version, distribution, license, end-user configuration, and npm.

95. Which database works best when used in conjunction with Node.js?

Some of the databases used with Node.js include Cassandra, CouchDB, MySQL, MongoDB, Neo4j, Oracle, PostgreSQL, and ElasticSearch.

96. Describe the Node.js reactor design paradigm.

The reactor design is responsible for the nonblocking I/O feature. Before an I/O request is made, the handler is sent to a demultiplexer that manages concurrency, gathering requests as events and executing these events in queues to prevent I/O blocking.

97. Explain the Node.js Buffer class.

The Node.js buffer class offers a method for controlling binary data sources.

98. What command should I use to install a package?

To include a program or module in a script file, use the required command.

99. How do callbacks work?

Node.js uses callback functions to handle event processing.

100. What in Node.js is a Promise?

A Promise is a stand-in for a value that isn’t always understood at the time the promise is made.

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Wrapping up

The most widely used platform for creating backend web services that interact with server-side databases like MongoDB or NoSQL is the runtime JavaScript environment Node.js.The development of scalable data-intensive networks and e-commerce apps that are event-driven and asynchronous is another area where Node.js is put to use.

Node.js Interview Questions and Answers FAQs:

Do Netflix’s backend coder interviews include Node.js interview questions?

You must thoroughly research the key Node.js concepts if you’re applying for a backend developer job at Netflix. It is used by Netflix to speed up development, reduce build delays, and increase the degree of user interface customization for each user.

Do front-end engineers need to prepare for Node.js interview questions?

As a backend framework, Node.js has grown in prominence. Today, many leading tech firms prefer using the Node.js front-end framework to create quick, effective network applications.