Node.js interview questions typically cover topics such as the event-driven architecture, non-blocking I/O, modules, streams, callbacks, and the Node.js ecosystem, helping assess a candidate’s understanding and proficiency in developing scalable and efficient server-side applications using JavaScript.
Q1. What is Node.js?
Ans. Node.js is the ideal open-source, cross-platform for developing server-side web applications. It is built on Google’s V8 JavaScript engine, and its package ecosystem (npm) is the most extensive core library. It is written in JavaScript and is the Libuv platform abstraction layer. Node.js works on a non-blocking I/O (input/output) model, which eases its functionality and improves speed and efficiency.
Q2. What are Node Modules?
Ans. It is known as the block of codes that don’t affect other codes. Node.js has built-in node modules that don’t require any installation.
Q3. How to write ‘Beautiful Life’ in Node.js?
Ans. Follow the below steps:
Create a file called app.js
Enter console.log (“learn NodeJS with Sumit Sharma !”);
Open node terminal
Change the directory to the folder
Run node app.jsQ4. Is there any difference between JavaScript and Node.js?
Ans. Below are some significant differences between JavaScript and Node.js:
| JavaScript | Node.js |
| It is a programming language | It works as an interpreter and environment for JavaScript |
| Runs on any web browser | Runs on V8 (Chrome) |
| Follows the standards of Java programming language | Node Js follows C++ |
| Used for web application’s client-side activity | Used for performing the non-blocking operation |
Q5. Which are the most popular Node.js frameworks you have used?
Ans. Below is the list of frameworks that I have used:
| Node.js Frameworks | Description |
| AdonisJs | Made up with SQL-database and supports No-SQL database including MongoDB |
| Express.js | Helps in managing servers and routes and building lightweight applications |
| Meteor.js | Assists in developing modern web and mobile applications |
| Nest.js | Helps in creating effective and scalable server-side Node.js applications |
| Sails.js | Assists in developing customized enterprise-grade applications and it is one of the highly recommended MVC node.js frameworks |
| Koa.js | Known as next-generation framework having ECMAScript (ES6) |
Q6. List some benefits of Node.js
Ans. Below are some benefits of Node.js:
| Node.js Benefits | |
| Scalable | Applications are easy to scale in horizontal and vertical directions |
| Single Language | It is one of the most efficient server-side JavaScript languages used for both front-end and back-end development. |
| Fullstack JS | It is helpful in both client-side and server-side language |
| High-performing language | It interprets JS code via Chrome’s V8 engine; hence it compiles JS code directly into the machine code and supports non-blocking I/O operations, which makes it a high-performing language |
| Cache benefits | It supports caching of every single module in the application memory |
| Supports Common tools | In Node.js, developers can get the support of commonly extended tools like Jasmin and unit-testing tools |
Q7. Did you find any drawbacks in node.js?
Ans. Node.js has a major drawback: the Application Programming Interface (API) is sometimes unstable.
Q8. Do you keep track of Node.js trends?
Ans. Yes, as a developer, it is essential to comprehend frequent updates. Below are some interesting facts that caught my attention:
Now node.js is a serverless and hardware-free solution that will enhance its performance and productivity.
Maintenance of code in node.js is easy because of the microservices it offers.
js is helpful in giving strong backend support to real-time apps because it is an excellent data-serving platform supporting WebSockets protocols.
js holds a key position in IoT due to its data-centric approaches.
Q9. Do you think Node.js is better than PHP?
Ans. Both PHP and Node.js offer excellent programming experience to both developers and end-users. The main differences are –
| PHP | Node.js |
| Supported by a good number of hosting platforms and is easy to use | It is more of a virtual server, and as it is younger than PHP, developers find it challenging to use |
| It provides a reliable and stable platform | Speedy and quick turnaround time |
| The platform is less flexible | The platform is highly flexible, agile, and scalable |
| Competent in handling CPU-intensive roles | Less effective in handling CPU-intense activities |
| Stuck when the number of codes is huge | Hardly gets stuck |
Q10. State some features of Node.js v12.
Ans. Recently node.js v12 was launched in 2019, and some of its key highlights are:
- The V8 version is updated to 7.4
- The default HTTP parser is now redirected to IIhttp
- A new feature is introduced called “Diagnostic Reports”
- The error message has witnessed an update which points to checking the specific errors and failures
- js supports TLS1.3 as a default max protocol
- js can now trace asynchronous call frames due to its Async stack traces updates
Q11. Name some node.js applications.
Ans. Node.js applications are used in the below-mentioned domains:
- Real-time applications
- Network applications
- Distributed systems
Q12. Name some companies that use node.js.
Ans. Some of the top companies using node.js are:
- PayPal
- Yahoo, Mozilla
- Netflix
- Uber
- eBay
- Medium
- NASA
- Trello
Q13. Which performance metrics do you track for node.js?
Ans. It is essential to track performance metrics and evaluate node.js applications, including websites, web apps, mobile apps, enterprise apps, etc. Some of the parameters that one must determine are:
| Metrics | Description |
| Event Loop | Checks the ability to execute code in a queue |
| Real-time behaviour | Checks the response time of real-time applications |
| External frameworks | Checks the response time, error rates, APIs, and request rates as node.js depends on several external frameworks |
| Process Memory | Measures the time spent and runs memory on the helper tool called Garbage Collector |
Q14. What is meant by Event-driven programming in Node.js?
Ans. Though node.js is a single-threaded programming application, it supports the concurrence of events and callbacks and uses an async function. Event-driven programming is designed on a concept to avoid collisions.
Whenever a user interacts on a webpage, an event recurs, and as a result, a change occurs on the user interface when an event triggers the associated function.
Q15. Which concepts are used in event-driven programming?
The following concepts are used in event-driven programming:
- The callback function is called whenever an event triggers.
- The main loop stays active, responds to each trigger, and calls the event handler for each event.
Q16. What do you mean by the Libuv platform?
Ans. It is a support library of Node.js and is a multi-platform used for asynchronous I/O. Some crucial features of Libuv are:
- Backed with the full-featured event loop
- Includes file system events
- Supports child processes
- Has asynchronous files & involves file system operations
- Includes asynchronous TCP & UDP sockets
Q17. Have you heard of callback hell? What is it?
Ans. In Node.js, callback hell is used to return heavily nested callbacks that are complex and unreadable.
Q18. Which strategy works well for handling callback hell?
Ans. To handle callback hell, the below steps can be helpful:
- Work on handling each error
- Maintain simple codes
- Split the complex codes into independent functions
Q19. What are API functions in node.js?
Ans. There are two types of functions:
- Blocking function – The codes are blocked till the time the I/O event occurs
- Non-blocking function – Several I/O calls are performed without blocking the entire program.
Q20. Name the different types of streams available in node.js.
Ans. Streams in Node.js are used to connect with each other to form a chain. There are four different types of streams in node.js:
<Readable>
<Writable>
<Duplex>
<Transform>
Q21. What do you mean by Globals?
Ans. Globals comprise of three different keywords:
- Global – It acts as a container for global objects representing the global namespace.
- Process – It is both a global object and an asynchronous function used to return information related to the application.
- Buffer – It handles binary data as it is a class
Q22. How unhandled are exceptions caught in Node.js?
Ans. Using “Process,” a handler is attached for the “uncaughtException” event.
Q23. Define the test pyramid.
Ans. It gives an optimum ratio of unit tests, integration tests, and end-to-end tests a developer should use.
Q24. Define the way to secure HTTP cookies from XSS attacks.
Ans. This situation arrives when the attacker injects the JavaScript code into an HTML response. To mitigate such an unacceptable risk, the below steps can help:
Set flags using “set-cookie” HTTP header – HttpOnly and secure
Use code Set-Cookie: Set=<cookie-value>; HttpOnly
Q25. Find an error in this code:
Challenges in Life((resolve, reject) => { point out Error (‘error’) }).then(console.log)
Ans. This code will retrieve no error indication because the ‘catch’ function is missing before the ‘then’ function.
Q26. Write code using module.exports in Node.js.
Ans. Below is the code:
module.exports = {
SayGoodNightInFrench; function () {
return “Bonne Nuit”;
},
sayGoodNightInGerman: function () {
Return “Gute Nacht”;
}
};
Q27. How will you import the above code into a different file?
Ans. Below is the code for importing the code in a different file:
var wishes = require(“ ./wishes.js”);
wishes. SayGoodNightInFrench(); // Bonne Nuit
wishes. sayGoodNightInGerman(); // Gute Nacht
Q28. Explain the term I/O.
Ans. I/O stands for Input/Output. It refers to the interaction of a program with the system’s disk and network. It represents any program, operation, or device that transfers data to or from one medium to another medium, such as a physical device, network, or files within a system.
Q29. Explain the control flow function.
Ans. The control flow function is a code that runs between several asynchronous function calls.
Q30. Name the arguments that async.queue takes as input.
Ans. The arguments are:
- Task Function
- Concurrency Value
Q31. What is the difference between Angular and Node.js?
| Angular Js | Node JS |
| Angular is an open-source web application development framework. | It is a cross-platform run-time environment and system for applications. |
| It is written in JavaScript. | Node.js is written in C, C++, and JavaScript programming languages. |
| AngularJS itself is a web application framework of JavaScript. | Node js has various frameworks such as Express.js, Sails.js, and Partial.js. |
| It is primarily used for creating single-page client-side web applications. | It is used for creating fast and scalable server-side networking applications. |
| Angular is suitable for building highly active and interactive web apps. | It is suitable for small-size projects. |
| It is based on the model-view-controller design pattern. | Node js is single-threaded. |
Q32. Name some exit codes of Node.js.
Ans. The following are some exit codes of Node.js:
- Unused
- Fatal Error
- Uncaught fatal exception
- Internal Exception handler Run-time failure
- Internal JavaScript Evaluation Failure
