NodeJs Interview Questions and Answers


NodeJs Interview Questions and Answers

INTRODUCTION– Node.js is a popular language which is used for server -side frameworks and it uses asynchronous non-blocking I/O model for handling client requests. As you are beginning the road of Node.js developer, it is crucial that you are familiar with basic concepts of Node.js so that you can display confidence and clarity while answering the questions regarding the language. In this article, we will discuss some questions which are commonly asked by panel of interviewers of Software companies. If you are looking for job in field of programming and Node.js interests you, then these are the questions which you can expect for assessing your knowledge. So, why wait?

Let us discuss some questions and answers-

  1. What is Node.js?

Node.js is a scripting language that handles the server side to build robust applications. It has multiple advantages over other frameworks, the prominent being non-blocking I/O.

  1. What does the term I/O mean?

It simply means input and output and it can be run on machine memory once the application is started. It will access everything outside the app.

  1. How does Node.js works?

It runs on Chrome V8 engine and makes use of non-blocking I/O model with single threaded event loop to generate efficient output by utilizing scripting language such as JavaScript.

  1. What do you mean by event driven programming?

In the world of programming, event driven programming is a way in which events such as threads or other messages direct the flow of program. The framework of the application is divided into Event selection and its handling.

  1. Explain the two types of API functions in Node.js?
  • Asynchronous, non-blocking mode.
  • Synchronous, blocking mode.
  1. What do you mean by control flow function?

During Asynchronous function calls, whenever a code runs in between, it is called control flow  function.

  1. Explain how control flow function works?


  • Manages the process of execution.
  • Retrieve data.
  • Limit concurrency
  • Call for next step.
  1. What are the tasks that can be done asynchronously while using event loop?
  • Huge computation
  • I/O operations.
  • Anything requiring blocking.


  1. Why is Node.js single threaded mechanism?

Node.js was initially created to test the concept of asynchronous processing and it was found that high performance and scalability could be achieved using single threaded loop for web load rather than using multiple threads for client’s requests.

  1. What are the steps by which you can Async in Node.js?

The steps are:

  • Functions of first class.
  • Call-back counters.
  • Event loops model.
  1. Which framework is used with Node.js?

Express framework is used normally with Node.js.

  1. How does “non-blocking “in Node.js work?

In Node.js, non-blocking I/O means that IO cannot be blocked under any circumstance. In this Node.js uses “libuv” libraries to initiate the requests generated by multiple clients through call back function which queues within the event loop function and thus generates the main JavaScript thread.


  1. Why Node.js is quickly garnering attention from the programmers?

Node.js gives the ability to user to code in JavaScript for server side which handles HTTP requests, file I/O and databases and it is quickly gaining attention as it is a loop based server.

  1. What challenges can you confront with Node.js?

In lieu of technological perspective, it is challenging to handle multiple requests from clients using single threaded loop.

  1. Explain “call back” function in Node.js.

“Call back” function is initiated when the server has to deal with several client requests. Assume that server has to access data for the large file and simultaneously it has also to process other requests which has been generated henceforth. So here the call back function is used in which server deals first with the pending request and then  carry on with the task .


  1. Analyse the pros and cons of Node.js.

PROS- If the application doesn’t use CPU intensive computation,then you can create your app with JavaScript in entirety.

Clients receives full HTML response which is far better than any single page application.

CONS-Node.js will not respond with CPU intensive communication.

It is generally not recommended to use relational databases with Node.js.


-During interviews, Companies analyse your understanding towards a certain concept and it can be obtained through certification course to prove your competency. Ace Softech Academy ,one of the best NodeJs training center in Kolkata, has skilled professionals that can accelerate Node.js skills with best industrial training.