Node.js is a super popular server-side platform that more and more organizations are using. If you are preparing for a career change and have an upcoming job interview, it’s always a good idea to prepare and brush up on your interview skills beforehand. Although there are a few commonly asked Node.js interview questions that pop up during all types of interviews, we also recommend that you prepare by focusing on exclusive questions for your specific industry.
Node.js is an incredibly robust framework built on Google Chrome’s JavaScript engine, which immediately converts JavaScript into native machine code. It is a small framework for developing server-side web-based apps that extends the JavaScript API to provide common server-side functionality. It is typically used for developing server software, large-scale programs, particularly online streaming websites, single-page apps, and other online applications.
Roles and responsibilities of a Node.js developer
You need a Node.js developer to fulfill the following responsibilities:
Understanding the business requirements and non-functional requirements (NFRs);
Studying the technical solutions;
Collaborating with the testing and DevOps teams to establish an effective “Continuous Integration” (CI)/”Continuous Delivery” (CD) environment;
Creating specifications for new Node.js applications;
Coding and unit-testing new apps;
Working with the testing and DevOps teams to test and deploy new Node.js apps;
Maintaining existing Node.js web applications;
Communicating effectively with all the relevant stakeholders;
Participating in process improvement initiatives.
Skills and competencies that you need in a Node.js developer
You need the following skills in a Node.js developer:
Knowledge of JavaScript;
Proficiency with Node.js and popular open-source tools and frameworks like Express.js;
Understanding of front-end technologies like HTML, HTML5, CSS, and CSS3;
Familiarity with server-side templating languages;
Knowledge of server-side CSS preprocessors;
Proficiency with popular software architecture patterns;
Experience with popular SQL databases like MySQL, PostgreSQL, etc.;
Knowledge of popular NoSQL databases like MongoDB, Cassandra, etc.;
Skills to develop RESTful APIs;
Experience in developing scalable web apps;
Knowledge of developing a Node js application that meets key NFRs like performance, security, maintainability, etc.;
Familiarity with cloud computing platforms;
The ability to create applications that support desktop and mobile users alike;
Knowledge of software engineering, code review, testing, and DevOps;
Familiarity with popular code versioning tools like Git.
We have compiled a comprehensive list of common Node Js interview questions that come up often in interviews and the best ways to answer these questions. This will also help you understand the fundamental concepts of Node.js.
Top NodeJs interview questions and answers
Check out the top NodeJs interview questions and answers for Freshers & Experienced Professionals:
1. What is a first class function in Javascript?
When functions can be treated like any other variable then those functions are first-class functions. There are many other programming languages, for example, scala, Haskell, etc which follow this including JS. Now because of this function can be passed as a param to another function(callback) or a function can return another function(higher-order function). map() and filter() are higher-order functions that are popularly used.
2. What is NodeJs and how it works?
Node.js is a virtual machine that uses JavaScript as its scripting language and runs Chrome’s V8 JavaScript engine. Basically, Node.js is based on an event-driven architecture where I/O runs asynchronously making it lightweight and efficient. It is being used in developing desktop applications as well with a popular framework called electron as it provides API to access OS-level features such as file system, network, etc.
3. How do you manage packages in your nodeJs project?
It can be managed by a number of package installers and their configuration file accordingly. Out of them mostly use npm or yarn. Both provide almost all libraries of javascript with extended features of controlling environment-specific configurations. To maintain versions of libs being installed in a project we use package.json and package-lock.json so that there is no issue in porting that app to a different environment.
4. How is Node.js better than other frameworks most popularly used?
Node.js provides simplicity in development because of its non-blocking I/O and even-based model results in short response time and concurrent processing, unlike other frameworks where developers have to use thread management.
It runs on a chrome v8 engine which is written in c++ and is highly performant with constant improvement.
Also since we will use Javascript in both the frontend and backend the development will be much faster.
And at last, there are ample libraries so that we don’t need to reinvent the wheel.
5. Explain the steps how “Control Flow” controls the functions calls?
Control the order of execution
Collect data
Limit concurrency
Call the following step in the program.
6. What are some commonly used timing features of Node.js?
setTimeout/clearTimeout – This is used to implement delays in code execution.
setInterval/clearInterval – This is used to run a code block multiple times.
setImmediate/clearImmediate – Any function passed as the setImmediate() argument is a callback that's executed in the next iteration of the event loop.
process.nextTick – Both setImmediate and process.nextTick appear to be doing the same thing; however, you may prefer one over the other depending on your callback’s urgency.
7. What are the advantages of using promises instead of callbacks?
The main advantage of using promise is you get an object to decide the action that needs to be taken after the async task completes. This gives more manageable code and avoids callback hell.
8. What is fork in node JS?
A fork in general is used to spawn child processes. In node it is used to create a new instance of v8 engine to run multiple workers to execute the code.
9. Why is Node.js single-threaded?
Node.js was created explicitly as an experiment in async processing. This was to try a new theory of doing async processing on a single thread over the existing thread-based implementation of scaling via different frameworks.
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10. How do you create a simple server in Node.js that returns Hello World?
var http = require("http"); http.createServer(function (request, response) { response.writeHead(200, {'Content-Type': 'text/plain'}); response.end('Hello World\n'); }).listen(3000);
11. How many types of API functions are there in Node.js?
There are two types of API functions:
Asynchronous, non-blocking functions - mostly I/O operations which can be fork out of the main loop.
Synchronous, blocking functions - mostly operations that influence the process running in the main loop.
12. What is REPL?
PL in Node.js stands for Read, Eval, Print, and Loop, which further means evaluating code on the go.
13. List down the two arguments that async.queue takes as input?
Task Function
Concurrency Value
14. What is the purpose of module.exports?
This is used to expose functions of a particular module or file to be used elsewhere in the project. This can be used to encapsulate all similar functions in a file which further improves the project structure.
For example, you have a file for all utils functions with util to get solutions in a different programming language of a problem statement.
const getSolutionInJavaScript = async ({ problem_id }) => { ... }; const getSolutionInPython = async ({ problem_id }) => { ... }; module.exports = { getSolutionInJavaScript, getSolutionInPython }
Thus using module.exports we can use these functions in some other file:
const { getSolutionInJavaScript, getSolutionInPython} = require("./utils")
15. What tools can be used to assure consistent code style?
ESLint can be used with any IDE to ensure a consistent coding style which further helps in maintaining the codebase.
That's all about common Node.js interview questions with Answers for 1 to 2 years experienced we, developers. Node.js alone is not a huge topic for interviews. In this article, we listed 15+ Node interview questions which include the combined question for freshers and experienced. I believe that these Node.js interview questions would help you understand what kind of questions may be asked to you in an interview, and by going through these Node.js interview questions, you can prepare and crack your next interview in one go. For more in-depth interview questions on NodeJs which can prepare you even more for any upcoming interviews.
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