Node.js Interview Questions and Answers, Node.js Interview Questions and Answers Freshers, Node.js Interview Questions and Answers, Node.js Interview Questions

Before getting on to the Node.js interview questions, the student must know that the Node.js is a continuously varying field which needs the students as well as professionals to upgrade their skills with the new features and knowledge, to get fit for the jobs associated with Node.js. This post related to Node.js Interview Questions and Answers, Node.js Interview Questions and Answers Freshers, Node.js Interview Questions and Answers, Node.js Interview Questions will help you let out find all the solutions that are frequently asked in you upcoming Node.js interview.

Over thousands of vacancies available for the Node.js developers, experts must be acquaintance with all the component of Node.js technologies. This is necessary for the students in order to have in-depth knowledge of the subject so that they can have best employment opportunities in the future. Knowing every little detail about Node.js is the best approach to solve the problems linked with problem.

APTRON has spent hours and hours in researching about the Node.js Interview Questions and Answers, Node.js Interview Questions and Answers Freshers, Node.js Interview Questions and Answers, Node.js Interview Questions that you might encounter in your upcoming interview.  All these questions will alone help you to crack the interview and make you the best among all your competitors.

First of all, let us tell you about how the Node.js technology is evolving in today’s world and how demanding it is in the upcoming years. In fact, according to one study, most of the companies and businesses have moved to the Node.js. Now, you cannot predict how huge the future is going to be for the people experienced in the related technologies.

Hence, if you are looking for boosting up your profile and securing your future, Node.js will help you in reaching the zenith of your career. Apart from this, you would also have a lot of opportunities as a fresher.

These questions alone are omnipotent. Read and re-read the questions and their solutions to get accustomed to what you will be asked in the interview. These Node.js interview questions and answers will also help you on your way to mastering the skills and will take you to the giant world where worldwide and local businesses, huge or medium, are picking up the best and quality Node.js professionals.

This ultimate list of best Node.js interview questions will ride you through the quick knowledge of the subject and topics like Mongo Shell, Using Eval, External Editor Integration, Saving Data, Set Operator. This Node.js interview questions and answers can be your next gateway to your next job as a Node.js expert.

These are very Basic Node.js Interview Questions and Answers for freshers and experienced both.

Q1: What is Node.js? Where can you use it?
A1: Node.js is a server side scripting based on Google’s V8 JavaScript engine. It is used to build scalable programs especially web applications that are computationally simple but are frequently accessed.

You can use Node.js in developing I/O intensive web applications like video streaming sites. You can also use it for developing: Real-time web applications, Network applications, General-purpose applications and Distributed systems.

Q2: Why is Node.js Single-threaded?
A2: Node.js is single-threaded for async processing. By doing async processing on a single-thread under typical web loads, more performance and scalability can be achieved as opposed to the typical thread-based implementation.

Q3: Explain callback in Node.js.
A3: A callback function is called at the completion of a given task. This allows other code to be run in the meantime and prevents any blocking. Being an asynchronous platform, Node.js heavily relies on callback. All APIs of Node are written to support callbacks.

Q4: Explain the role of REPL in Node.js.
A4: As the name suggests, REPL (Read Eval print Loop) performs the tasks of – Read, Evaluate, Print and Loop. The REPL in Node.js is used to execute ad-hoc Javascript statements. The REPL shell allows entry to javascript directly into a shell prompt and evaluates the results. For the purpose of testing, debugging, or experimenting, REPL is very critical.

Q5: What are the functionalities of NPM in Node.js?
A5: NPM (Node package Manager) provides two functionalities:

  • Online repository for Node.js packages
  • Command line utility for installing packages, version management and dependency management of Node.js packages

Q6: Explain chaining in Node.js.
A6: Chaining is a mechanism whereby the output of one stream is connected to another stream creating a chain of multiple stream operations.

Q7: What are exit codes in Node.js? List some exit codes.
A7: Exit codes are specific codes that are used to end a “process” (a global object used to represent a node process).

Examples of exit codes include:

  • Unused
  • Uncaught Fatal Exception
  • Fatal Error
  • Non-function Internal Exception Handler
  • Internal Exception handler Run-Time Failure
  • Internal JavaScript Evaluation Failure

Q8: What are Globals in Node.js?
A8: Three keywords in Node.js constitute as Globals. These are:

  • Global – it represents the Global namespace object and acts as a container for all otherobjects.
  • Process – It is one of the global objects but can turn a synchronous function into an async callback. It can be accessed from anywhere in the code and it primarily gives back information about the application or the environment.
  • Buffer – it is a class in Node.js to handle binary data.

Q9: Is it free to use Node.js?
A9: Yes! Node.js is released under the MIT license and is free to use.

Q10: Is Node a single threaded application?
A10: Yes! Node uses a single threaded model with event looping.

Q11: What is Package.json?
A11: package.json is present in the root directory of any Node application/module and is used to define the properties of a package.

Q12: Name some of the attributes of package.json?
A12: Following are the attributes of Package.json

  • name – name of the package
  • version – version of the package
  • description – description of the package
  • homepage – homepage of the package
  • author – author of the package
  • contributors – name of the contributors to the package
  • dependencies – list of dependencies. npm automatically installs all the dependencies mentioned here in the node_module folder of the package.
  • repository – repository type and url of the package
  • main – entry point of the package
  • keywords – keywords

Q13: How Node prevents blocking code?
A13: By providing callback function. Callback function gets called whenever corresponding event triggered.

Q14: What is Event Loop?
A14: Node js is a single threaded application but it support concurrency via concept of event and callbacks. As every API of Node js are asynchronous and being a single thread, it uses async function calls to maintain the concurrency. Node uses observer pattern. Node thread keeps an event loop and whenever any task get completed, it fires the corresponding event which signals the event listener function to get executed.

Q15: What are streams?
A15: Streams are objects that let you read data from a source or write data to a destination in continous fashion.

Q16: How many types of streams are present in Node.
A16: In Node.js, there are four types of streams.

  • Readable – Stream which is used for read operation.
  • Writable – Stream which is used for write operation.
  • Duplex – Stream which can be used for both read and write operation.
  • Transform – A type of duplex stream where the output is computed based on input.

Q17: What is the purpose of setTimeout function?
A17: The setTimeout(cb, ms) global function is used to run callback cb after at least ms milliseconds. The actual delay depends on external factors like OS timer granularity and system load. A timer cannot span more than 24.8 days.

This function returns an opaque value that represents the timer which can be used to clear the timer.

Q18: What is the purpose of clearTimeout function?
A18: The clearTimeout( t ) global function is used to stop a timer that was previously created with setTimeout(). Here t is the timer returned by setTimeout() function.

Q19: What are the two types of API functions in Node.js ?
A19: The two types of API functions in Node.js are

a) Asynchronous, non-blocking functions
b) Synchronous, blocking functions

Q20: Why node.js is quickly gaining attention from JAVA programmers?
A20: Node.js is quickly gaining attention as it is a loop based server for JavaScript. Node.js gives user the ability to write the JavaScript on the server, which has access to things like HTTP stack, file I/O, TCP and databases.

Q21: What are the pros and cons of Node.js?
A21: Pros:

a) If your application does not have any CPU intensive computation, you can build it in Javascript top to bottom, even down to the database level if you use JSON storage object DB like MongoDB.
b) Crawlers receive a full-rendered HTML response, which is far more SEO friendly rather than a single page application or a websockets app run on top of Node.js.


a) Any intensive CPU computation will block node.js responsiveness, so a threaded platform is a better approach.
b) Using relational database with Node.js is considered less favourable

Q22: Mention the framework most commonly used in node.js?
A22: “Express” is the most common framework used in node.js

Q23: What is ‘Callback’ in node.js?
A23: Callback function is used in node.js to deal with multiple requests made to the server. Like if you have a large file which is going to take a long time for a server to read and if you don’t want a server to get engage in reading that large file while dealing with other requests, call back function is used. Call back function allows the server to deal with pending request first and call a function when it is finished.

Q24: What is the latest version of Node.js available?
A24: Latest version of Node.js is – v0.10.36.

Q25: Mention the command to stop REPL in Node.js?
A25: Command – ctrl + c twice is used to stop REPL.

Q26: Explain “Buffer class” in Node.JS?
A26: It is a global class which can be accessed in an application without importing buffer modules.

Q27: How to concatenate buffers in NodeJS?
A27: The syntax to concatenate buffers in NodeJS is
var MyConctBuffer = Buffer.concat([myBuffer1, myBuffer2]);

Q28: What are the differences between “readUIntBE” and “writeIntBE” in Node.JS?

  • readUIntBE – It’s a generalized version of all numeric read methods, which supports up to 48 bits accuracy. Setting noAssert to “true” to skip the validation.
  • writeIntBE – This will write the value to the buffer at the specified byteLength and offset and it supports upto 48 bits of accuracy.

Q29: List out the layers involved in Web App Architechure?
A29: Below are the layers used in Web Apps –

  • Client – Which makes HTTP request to the server. Eg: Browsers.
  • Server – This layer is used to intercept the requests from client.
  • Business – It will have application server utilized by web servers for processing.
  • Data – This layer will have databases mainly or any source of data.

Q30: Does Node.Js Support Multi-Core Platforms? And Is It Capable Of Utilizing All The Cores?
A30: Yes, Node.js would run on a multi-core system without any issue. But it is by default a single-threaded application, so it can’t completely utilize the multi-core system.

However, Node.js can facilitate deployment on multi-core systems where it does use the additional hardware. It packages with a Cluster module which is capable of starting multiple Node.js worker processes that will share the same port.

Q31: What Is A Child_process Module In Node.Js?
A31: Node.js supports the creation of child processes to help in parallel processing along with the event-driven model.

The Child processes always have three streams , child.stdout, and child.stderr. The stream of the parent process shares the streams of the child process.

Node.js provides a module which supports following three methods to create a child process.

  • exec – <child_process.exec> method runs a command in a shell/console and buffers the output.
  • spawn – <child_process.spawn> launches a new process with a given command.
  • fork – <child_process.fork> is a special case of the spawn() method to create child processes.

Node.js Conclusion Interview FAQs

We know the list of Node.js Interview Questions and Answers, Node.js Interview Questions and Answers Freshers, Node.js Interview Questions and Answers, Node.js Interview Questions is overwhelming but the advantages of reading all the questions will maximize your potential and help you crack the interview. The surprising fact is that this Node.js interview questions and answers post covers all the basic of the Node.js technology and you have to check out the FAQs of different components of Node.js too.

However, you will be asked with the questions in the interview related to the above mentioned questions. Preparing and understanding all the concept of Node.js technology will help you strengthen the other little information around the topic.

After preparing these interview questions, we recommend you to go for a mock interview before facing the real one. You can take the help of your friend or a Node.js expert to find the loop holes in your skills and knowledge. Moreover, this will also allow you in practicing and improving the communication skill which plays a vital role in getting placed and grabbing high salaries.

Remember, in the interview, the company or the business or you can say the examiner often checks your basic knowledge of the subject. If your basics is covered and strengthened, you can have the job of your dream. The industry experts understand that if the foundation of the student is already made up, it is easy for the company to educate the employ towards advance skills. If there are no basics, there is no meaning of having learnt the subject.

Therefore, it’s never too late to edge all the basics of any technology. If you think that you’ve not acquired the enough skills, you can join our upcoming batch of Node.js Training in Noida. We are one of the best institute for Node.js in noida which provide advance learning in the field of Node.js Course. We’ve highly qualified professionals working with us and promise top quality education to the students.

We hope that you enjoyed reading Node.js Interview Questions and Answers, Node.js Interview Questions and Answers Freshers, Node.js Interview Questions and Answers, Node.js Interview Questions and all the FAQs associated with the interview. Do not forget to revise all the Node.js interview questions and answers before going for the Node.js interview. In addition to this, if you’ve any doubt or query associated with Node.js, you can contact us anytime. We will be happy to help you out at our earliest convenience. At last, we wish you all the best for your upcoming interview on Node.js Technology.