Top Node.js Interview Questions You Must Prepare In 2018

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Mar 17, 2016
Top Node.js Interview Questions You Must Prepare In 2018
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Node.js, the server-side scripting tool, uses JavaScript – a language that is popular with millions of developers worldwide – ensuring that it has a much lower learning curve even for complete beginners. Using Node.js, one can build everything from simple command line programs to complex enterprise level web applications with equal ease. Node.js, also brings with it, career opportunities at various levels. In case you are planning to attend Node.js interviews in the near future, we are here to help you with a list of Node.js interview questions and answers.

If you have attended Node.js interviews in the recent past, do paste your questions in the comments tab below and we’ll be happy to get our technical teams to answer them.

 Node.js Interview Questions

1. What is Node.js?

Wikipedia defines Node.js as “an open-source, cross-platform runtime environment for developing server-side Web applications.” It is essentially server side scripting which is used to build scalable programs.

2. What is the relation of Node.js with JavaScript? 

Though Node.js is not a JavaScript framework,[3] many of its modules are written in JavaScript, allowing developers to create new modules in JavaScript.   Node.js is a virtual machine that leverages JavaScript as its scripting language to achieve high output.

3. What is the fundamental difference between Node.js and Ajax?

While Ajax is a client-side technology, Node.js is a server-side JavaScript environment.

4. Explain the term I/O in the context of Node.js.

I/O stands for input and output. It is used to access anything outside of the application. I/O gets loaded on to the machine memory in order to run programs after the application is fired up.

5. State where Node.js can be used.

  • Web apps
  • Network applications
  • Distributed systems
  • General purpose applications

6. Which are the two types of API functions in Node.js?

Asynchronous, non-blocking functions and Synchronous, blocking functions.

7. List the tools and IDEs that are used for Node.js.

  • Atom
  • Nodeclipse Enide Studio
  • JetBrains WebStorm
  • JetBrains InteliJ IDEA
  • MS Visual Studio
  • NoFLo

8. Explain the role of the Callback function in Node.js.

In Node.js, the Callback function is used to cater to multiple requests made to the server. If there is a large file that is expected to take the server a long time to process, the Callback function can be invoked to ensure that other requests to the server are uninterrupted.

9. What is an error-first callback?

Error-first callbacks are essentially used to pass errors and data. By default, the first argument is always an error object, where the user needs to check if something is wrong.

10. In the context of Node.js, differentiate between operational and programmer errors.

Operational errors are not real errors. They are system errors, for example “request timeout” or “hardware error”. Programmer errors are actual bugs in the code.

11. Which is the framework that is most commonly used in Node.js?

The most commonly used Node.js framework is “Express”.

12. Define “event-driven programming.

It is essentially a programming paradigm where the program flow is characterized by events such as messages from other programs.

13. What are the two sections of event-driven programming?

Event Selection and Event Handling are two sections of event-driven programming.

14. List some of the big advantages of using Node.js.

  • Ability to build scalable programs
  • Increased concurrency
  • Asynchronous capabilities

15. Explain the Control Flow function.

It is a generic piece of code that runs concurrently between several asynchronous function calls.

16. List the steps involved in the Control Flow function.

Control the order of execution à Collect data à Limit concurrency à Call the next program step

17. Can a user access DOM in a Node?

No, you cannot access DOM.

18. In Node.js, how do you access the last expression?

We have to use the underscore (_) character to access the last expression.

19. In Node.js, which command is used to import external libraries?

A command called “require” is used for importing external libraries.

20. What is the biggest drawback of Node.js?

The biggest drawback is the fact that it is challenging to have one process with a single thread to scale up on multi core servers.

Got a question for us? Please mention it in the comments section and we will get back to you.

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  • Girish

    elaborate event-driven programming with an example

    • EdurekaSupport

      Hey Girish, thanks for checking out our blog. Node.js uses events heavily and it is also one of the reasons why Node.js is pretty fast compared to other similar technologies. As soon as Node starts its server, it simply initiates its variables, declares functions and then simply waits for the event to occur.
      In an event-driven application, there is generally a main loop that listens for events, and then triggers a callback function when one of those events is detected.
      Now create a program and name it as sample.js

      // Import events module
      var events = require(‘events’);

      // Create an eventEmitter object
      var eventEmitter = new events.EventEmitter();

      // Create an event handler as follows
      var connectHandler = function connected() {
      console.log(‘connection succesful.’);

      // Fire the data_received event

      // Bind the connection event with the handler
      eventEmitter.on(‘connection’, connectHandler);

      // Bind the data_received event with the anonymous function
      eventEmitter.on(‘data_received’, function(){
      console.log(‘data received succesfully.’);

      // Fire the connection event

      console.log(“Program Ended.”);

      Now run the code

      $ mnode sample.js

      Now the output will be :-

      connection successful.
      data received successfully.
      Program Ended.

      Hope this helps. Cheers!

  • Swati Sonam

    Thanks. Really helpful

    • EdurekaSupport

      Thanks Swati. We are so happy we could help. Do keep checking back in for more blogs on all your favourite topics.