Lesson 7 of 7By Taha Sufiyan
Last updated on Apr 9, 2021134628Node.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 to your specific industry.
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.
The Node.js interview questions are grouped into the following categories:
Node.js is an open-source, cross-platform JavaScript runtime environment and library to run web applications outside the client’s browser. It is used to create server-side web applications.
Node.js is perfect for data-intensive applications as it uses an asynchronous, event-driven model. You can use I/O intensive web applications like video streaming sites. You can also use it for developing: Real-time web applications, Network applications, General-purpose applications, and Distributed systems.
Node.js makes building scalable network programs easy. Some of its advantages include:
A web server using Node.js typically has a workflow that is quite similar to the diagram illustrated below. Let’s explore this flow of operations in detail.
A single thread from the Thread Pool is assigned to a single complex request. This thread is responsible for completing a particular blocking request by accessing external resources, such as computation, database, file system, etc.
Once the task is carried out completely, the response is sent to the Event Loop that sends that response back to the client.
Node.js is single-threaded for async processing. By doing async processing on a single-thread under typical web loads, more performance and scalability can be achieved instead of the typical thread-based implementation.
A callback function is called after a given task. It allows other code to be run in the meantime and prevents any blocking. Being an asynchronous platform, Node.js heavily relies on callback. All APIs of Node are written to support callbacks.
Node.js is widely used in the following applications:
Front-end |
Back-end |
Frontend refers to the client-side of an application |
Backend refers to the server-side of an application |
It is the part of a web application that users can see and interact with |
It constitutes everything that happens behind the scenes |
It typically includes everything that attributes to the visual aspects of a web application |
It generally includes a web server that communicates with a database to serve requests |
HTML, CSS, JavaScript, AngularJS, and ReactJS are some of the essentials of frontend development |
Java, PHP, Python, and Node.js are some of the backend development technologies |
NPM stands for Node Package Manager, responsible for managing all the packages and modules for Node.js.
Node Package Manager provides two main functionalities:
Modules are like JavaScript libraries that can be used in a Node.js application to include a set of functions. To include a module in a Node.js application, use the require() function with the parentheses containing the module's name.
Node.js has many modules to provide the basic functionality needed for a web application. Some of them include:
Core Modules |
Description |
HTTP |
Includes classes, methods, and events to create a Node.js HTTP server |
util |
Includes utility functions useful for developers |
fs |
Includes events, classes, and methods to deal with file I/O operations |
url |
Includes methods for URL parsing |
query string |
Includes methods to work with query string |
stream |
Includes methods to handle streaming data |
zlib |
Includes methods to compress or decompress files |
Some of the reasons why Node.js is preferred include:
Angular |
Node.js |
It is a frontend development framework |
It is a server-side environment |
It is written in TypeScript |
It is written in C, C++ languages |
Used for building single-page, client-side web applications |
Used for building fast and scalable server-side networking applications |
Splits a web application into MVC components |
Generates database queries |
MongoDB is the most common database used with Node.js. It is a NoSQL, cross-platform, document-oriented database that provides high performance, high availability, and easy scalability.
There are two commonly used libraries in Node.js:
Node.js Pros |
Node.js Cons |
Fast processing and an event-based model |
Not suitable for heavy computational tasks |
Uses JavaScript, which is well-known amongst developers |
Using callback is complex since you end up with several nested callbacks |
Node Package Manager has over 50,000 packages that provide the functionality to an application |
Dealing with relational databases is not a good option for Node.js |
Best suited for streaming huge amounts of data and I/O intensive operations |
Since Node.js is single-threaded, CPU intensive tasks are not its strong suit |
The “require” command is used for importing external libraries. For example - “var http=require (“HTTP”).” This will load the HTTP library and the single exported object through the HTTP variable.
Now that we have covered some of the important beginner-level Node.js interview questions let us look at some of the intermediate level Node.js interview questions.
An event-driven programming approach uses events to trigger various functions. An event can be anything, such as typing a key or clicking a mouse button. A call-back function is already registered with the element executes whenever an event is triggered.
Event loops handle asynchronous callbacks in Node.js. It is the foundation of the non-blocking input/output in Node.js, making it one of the most important environmental features.
The two types of API functions in Node.js are:
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The package.json file is the heart of a Node.js system. This file holds the metadata for a particular project. The package.json file is found in the root directory of any Node application or module
This is what a package.json file looks like immediately after creating a Node.js project using the command: npm init
You can edit the parameters when you create a Node.js project.
The URL module in Node.js provides various utilities for URL resolution and parsing. It is a built-in module that helps split up the web address into a readable format.
Express is a flexible Node.js web application framework that provides a wide set of features to develop both web and mobile applications
Streams are objects that enable you to read data or write data continuously.
There are four types of streams:
Readable – Used for reading operations
Writable − Used for write operations
Duplex − Can be used for both reading and write operations
Transform − A type of duplex stream where the output is computed based on input
As shown below, the async code asks the JavaScript engine running the code to wait for the request.get() function to complete before moving on to the next line for execution.
A module in Node.js is used to encapsulate all the related codes into a single unit of code, which can be interpreted by shifting all related functions into a single file. You can export a module using the module.exports, which allows it to be imported into another file using a required keyword.
A callback is a function called after a given task. This prevents any blocking and enables other code to run in the meantime.
In the last section, we will now cover some of the advanced-level Node.js interview questions.
REPL stands for Read Eval Print Loop, and it represents a computer environment. It’s similar to a Windows console or Unix/Linux shell in which a command is entered. Then, the system responds with an output
The control flow function is a piece of code that runs in between several asynchronous function calls.
fork() |
spawn() |
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fork() is a particular case of spawn() that generates a new instance of a V8 engine. |
Spawn() launches a new process with the available set of commands. |
Multiple workers run on a single node code base for multiple tasks. |
This method doesn’t generate a new V8 instance, and only a single copy of the node module is active on the processor. |
Buffer class stores raw data similar to an array of integers but corresponds to a raw memory allocation outside the V8 heap. Buffer class is used because pure JavaScript is not compatible with binary data
Piping is a mechanism used to connect the output of one stream to another stream. It is normally used to retrieve data from one stream and pass output to another stream
A reactor pattern is a concept of non-blocking I/O operations. This pattern provides a handler that is associated with each I/O operation. As soon as an I/O request is generated, it is then submitted to a demultiplexer
Middleware is a function that receives the request and response objects. Most tasks that the middleware functions perform are:
HTTP defines a set of request methods used to perform desired actions. The request methods include:
GET: Used to retrieve the data
POST: Generally used to make a change in state or reactions on the server
HEAD: Similar to the GET method, but asks for the response without the response body
DELETE: Used to delete the predetermined resource
To create a database in MongoDB:
As you prepare for your upcoming job interview, we hope that this comprehensive guide has provided more insight into what types of questions you’ll be asked.
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 training on this increasingly popular web application development framework, enroll in Simplilearn’s Node.js Training course today, which can prepare you even more for any upcoming Node.js interviews.
Best of luck with your upcoming job interview!
Taha is a Research Analyst at Simplilearn. He is passionate about building great user interfaces and keeps himself updated on the world of Artificial Intelligence. Taha is also interested in gaming and photography.
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