Published on Feb 26,2019
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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, most industries demand a Certified Node.js Developer to manage the entire server side. 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.

Features of Node JS

FastNode.js is built on Google Chrome’s V8 JavaScript Engine which makes its library very fast in code execution
AsynchronousNode.js based server never waits for an API to return data thus making it asynchronous
 ScalableIt is highly scalable because of its event mechanism which helps the server to respond in a non-blocking way
Open SourceNode.js has an extensive open source community which has contributed in producing some excellent modules to add additional capabilities to Node.js applications
No BufferingNode.js applications simply output the data in chunks and never buffer any data. 

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

  • Though Node.js is not a JavaScript framework, many of its modules are written in JavaScript.
  • It allows the 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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Published on Feb 26,2019

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