100+ Node JS Developer Interview Questions and Answers

Caching can be implemented using RabbitMQ by storing frequently accessed data in memory.

• Set up a RabbitMQ server to act as a message broker

• Publish data to RabbitMQ when it is fetched from the database

• Subscribe to messages in your Node.js application and store the data in memory

• Check the cache before fetching data from the database

Promises and callback functions are used in Node.js for handling asynchronous operations.

• Callback functions are functions passed as arguments to another function to be executed later.

• Promises are objects representing the eventual completion or failure of an asynchronous operation.

• Example of callback function: fs.readFile('file.txt', (err, data) => { if (err) throw err; console.log(data); });

• Example of promise: const readFile = new Promise((resolve, reject) => { fs.readFile('f...read more

Async await in Node.js is a feature that allows you to write asynchronous code in a synchronous manner.

• Async await is built on top of Promises in Node.js.

• It allows you to write asynchronous code that looks like synchronous code, making it easier to read and maintain.

• The 'async' keyword is used to define a function as asynchronous, while the 'await' keyword is used to wait for a Promise to resolve before continuing.

• Using async await can help avoid callback hell and make error ...read more

Node.js is a JavaScript runtime built on Chrome's V8 JavaScript engine. It allows developers to run JavaScript on the server-side.

• Node.js is event-driven and non-blocking I/O model.

• It uses an event loop to handle asynchronous operations.

• The event loop is a continuously running process that waits for events and executes callbacks.

• Callbacks are functions that are called when an event occurs, such as a request completing or a file being read.

• Node.js uses the libuv library to han...read more

A module in Angular is defined using the NgModule decorator.

• Import the NgModule decorator from @angular/core

• Use the decorator to define the module and its properties

• Export the module to make it available for other modules to import

Closures in JavaScript are functions that have access to their own scope, as well as the scope in which they were defined.

• Closures allow functions to access variables from an outer function even after the outer function has finished executing.

• They are created whenever a function is defined within another function.

• Closures are commonly used to create private variables and functions in JavaScript.

Experience with both relational and non-relational databases is essential for a Node JS Developer.

• Experience with relational databases like MySQL, PostgreSQL, etc.

• Experience with non-relational databases like MongoDB, Cassandra, etc.

• Understanding of when to use each type of database based on the project requirements.

• Ability to design database schemas and optimize queries for performance.

• Knowledge of data modeling and normalization in relational databases.

• Familiarity with docu...read more

AWS queues are messaging services that decouple components of a cloud application.

• Amazon SQS (Simple Queue Service) - fully managed message queuing service

• Amazon SNS (Simple Notification Service) - pub/sub messaging service

• Amazon MQ - managed message broker service

• Amazon Kinesis - real-time data streaming service

A promise is an object representing the eventual completion or failure of an asynchronous operation.

• Promises are used to handle asynchronous operations in JavaScript.

• They can be created using the Promise constructor.

• Promises have three states: pending, fulfilled, or rejected.

• They can be chained using .then() and .catch() methods.

• Example: const myPromise = new Promise((resolve, reject) => { ... });

libuv is a multi-platform support library with a focus on asynchronous I/O.

• libuv provides event loop, thread pool, timer, and file system APIs.

• It is used by Node.js to handle I/O operations in a non-blocking way.

• libuv abstracts the differences between operating systems and provides a consistent API.

• It also supports network programming and inter-process communication.

• Examples of libuv-based applications include Node.js, Atom, and Visual Studio Code.

A program to validate parentheses in a string using a stack in JavaScript

• Create an empty stack to store opening parentheses

• Iterate through the string and push opening parentheses onto the stack

• When a closing parenthesis is encountered, pop from the stack and check if it matches the corresponding opening parenthesis

• If stack is empty at the end and all parentheses are matched, return true

Middleware functions are functions that have access to the request object, response object, and the next middleware function in the application's request-response cycle.

• Middleware functions can perform tasks such as logging, authentication, error handling, etc.

• They are added to the application using the 'app.use()' method in Express.js.

• Error handling middleware functions typically have four parameters: (err, req, res, next).

• Example: app.use((err, req, res, next) => { console....read more

Node.js is a runtime environment that allows you to run JavaScript on the server side.

• Node.js allows developers to use JavaScript to write server-side code

• It uses an event-driven, non-blocking I/O model that makes it lightweight and efficient

• Node.js is commonly used for building web applications, APIs, and real-time applications

Nodejs is a server-side runtime environment while Angularjs is a client-side JavaScript framework.

• Nodejs is used for building server-side applications while Angularjs is used for building client-side applications.

• Nodejs is based on JavaScript and uses an event-driven, non-blocking I/O model.

• Angularjs is a framework for building dynamic web applications using HTML, CSS, and JavaScript.

• Nodejs is used for creating APIs, handling requests, and managing databases.

• Angularjs is used...read more

I'm sorry, but the question is not related to the job position of Node JS Developer.

• The question is not relevant to the job position.

• It is important to stay focused on the job requirements.

• If you are unsure about a question, it is okay to ask for clarification.

Callback hell is a situation in asynchronous JavaScript programming where multiple nested callbacks make the code difficult to read and maintain.

• Occurs when multiple asynchronous operations are nested within each other

• Leads to deeply nested code structure which is hard to read and debug

• Can be avoided by using promises, async/await, or modularizing code

The event loop in Node.js is a mechanism that allows Node.js to perform non-blocking I/O operations.

• The event loop is responsible for handling asynchronous operations in Node.js.

• It allows Node.js to perform I/O operations without blocking the execution of other code.

• The event loop continuously checks for tasks in the event queue and executes them in a non-blocking manner.

• Callbacks are used to handle the completion of asynchronous tasks in Node.js.

To scale an app for more users, consider optimizing code, using caching, load balancing, and horizontal scaling.

• Optimize code for better performance

• Implement caching to reduce database load

• Use load balancing to distribute traffic evenly

• Consider horizontal scaling by adding more servers

• Use microservices architecture for better scalability

Node.js is a runtime environment that allows developers to run JavaScript on the server side.

• Node.js is built on Chrome's V8 JavaScript engine, providing fast performance.

• It uses an event-driven, non-blocking I/O model, making it efficient for handling multiple connections.

• Node.js has a large ecosystem of libraries and packages available through npm, making it easy to build scalable applications.

• It is commonly used for building real-time web applications, APIs, and microservi...read more

There are two types of classes in Node JS: ES6 classes and prototype-based classes.

• ES6 classes are introduced in ES6 (ECMAScript 2015) and provide a more familiar syntax for class-based object-oriented programming.

• Prototype-based classes are the traditional way of defining classes in JavaScript, using prototypes to create objects and inherit properties and methods.

There are two types of functions in JavaScript: named functions and anonymous functions.

• Named functions are defined with a function name, such as function myFunction() {}

• Anonymous functions are defined without a function name, such as const myFunction = function() {}

Developed a real-time chat application using Node JS and Socket.io

• Used Node JS for server-side development

• Implemented Socket.io for real-time communication between clients and server

• Used MongoDB for storing chat messages

• Implemented authentication and authorization using Passport JS

• Used Bootstrap and jQuery for front-end development

Node.js is a runtime environment that allows you to run JavaScript on the server side.

• Node.js is built on Chrome's V8 JavaScript engine.

• It is lightweight and efficient for building scalable network applications.

• Node.js uses an event-driven, non-blocking I/O model, making it ideal for real-time applications like chat apps or streaming services.

Create a REST API in Express.js

• Install Express.js using npm

• Set up routes for different HTTP methods (GET, POST, PUT, DELETE)

• Use middleware for request processing

• Connect to a database to store and retrieve data

• Return JSON responses for API endpoints

Redux is a predictable state container for JavaScript apps. Redux Toolkit is the official, recommended way to write Redux logic.

• Redux is a state management library for JavaScript applications, commonly used with React.

• It helps in managing the state of an application in a predictable way.

• Redux Toolkit is the official, recommended way to write Redux logic, providing utilities to simplify common Redux use cases.

• It includes functions like 'createSlice' for defining Redux state sl...read more

I have worked on a real-time chat application and a RESTful API using Node JS.

• Developed a real-time chat application using Socket.io

• Built a RESTful API for a blogging platform

• Implemented authentication and authorization using JWT tokens

Cyclic dependency in Node.js occurs when two or more modules require each other, creating a loop that prevents the modules from being loaded correctly.

• Cyclic dependencies can lead to runtime errors or infinite loops in Node.js applications.

• To avoid cyclic dependencies, it is recommended to refactor the code to remove the circular references.

• One common solution is to use dependency injection or event-driven architecture to decouple modules.

Pharmacovigilance is the science and activities related to the detection, assessment, understanding, and prevention of adverse effects or any other drug-related problems.

• Pharmacovigilance is the process of monitoring and evaluating the safety and efficacy of drugs.

• It involves collecting and analyzing data on adverse drug reactions and other drug-related problems.

• Pharmacovigilance helps to ensure that drugs are safe and effective for use by patients.

• Examples of pharmacovigilan...read more

Terraform is used to automate infrastructure provisioning and management.

• Terraform is a tool for defining and provisioning infrastructure as code.

• It allows you to create, modify, and destroy infrastructure resources using declarative configuration files.

• Terraform supports various cloud providers like AWS, Azure, and GCP.

• You can define infrastructure resources such as virtual machines, networks, and storage using Terraform's domain-specific language (DSL).

• Terraform provides a ...read more

To setup a Node.js server, you need to install Node.js, create a server file, write code to create a server, and run the server.

• Install Node.js on your machine

• Create a server file (e.g. server.js)

• Write code to create a server using the 'http' module

• Run the server using the command 'node server.js'

require is used in Node.js to include modules and packages in a file.

• Used to include modules and packages in a file

• Helps in modularizing code and reusing functionality

• Loads the module and returns its exports object

Node.js applications can be deployed using various methods such as using a hosting service, containerization, or serverless platforms.

• Use a hosting service like Heroku, AWS, or DigitalOcean to deploy the application.

• Containerize the application using Docker and deploy it on a container orchestration platform like Kubernetes.

• Utilize serverless platforms like AWS Lambda or Google Cloud Functions for deploying serverless Node.js applications.

Shallow copy only copies the references of nested objects, while deep copy creates new copies of nested objects.

• Shallow copy creates a new object, but does not create copies of nested objects. Changes in nested objects reflect in both original and shallow copied objects.

• Deep copy creates a new object and also creates copies of nested objects. Changes in nested objects do not reflect in the original object.

package.json is a file used to manage dependencies and metadata of a Node.js project.

• It contains information about the project such as name, version, description, author, and license.

• It lists all the dependencies required for the project to run.

• It allows for the installation of all dependencies with a single command.

• It can also include scripts to automate tasks such as testing and building the project.

• It is located in the root directory of the project.

Event loop in Node.js is a mechanism that allows Node.js to perform non-blocking I/O operations.

• Event loop is responsible for handling asynchronous operations in Node.js.

• It allows Node.js to perform multiple operations concurrently without blocking the execution.

• Event loop continuously checks the event queue for any pending events and executes them in a loop.

• Example: When reading a file in Node.js, the event loop allows other operations to continue while waiting for the file ...read more

Implementing game logic in Node.js

• Break down the game logic into smaller functions

• Use event-driven programming to handle user input and game events

• Implement game mechanics such as scoring, levels, and game over conditions

• Handle game state and update it based on user actions

• Use data structures like arrays or objects to represent game elements

Node.js is a runtime environment that allows you to run JavaScript on the server side.

• Node.js is built on Chrome's V8 JavaScript engine.

• It uses an event-driven, non-blocking I/O model.

• Node.js is commonly used for building scalable network applications.

The '==' operator checks for equality, while the '===' operator checks for strict equality (including data type).

• The '==' operator performs type coercion before comparing two values.

• The '===' operator does not perform type coercion and compares both value and data type.

• Example: 1 == '1' will return true, but 1 === '1' will return false.

Non-blocking means that the execution of code does not stop to wait for a response, allowing other code to run simultaneously.

• Node.js uses an event-driven, non-blocking I/O model.

• Asynchronous functions in Node.js allow for non-blocking behavior.

• Callbacks are commonly used in Node.js to handle asynchronous operations.

• Example: Reading a file in Node.js does not block the execution of other code.

A callback function in Node.js is a function passed as an argument to another function, which will be executed at a later time.

• Callback functions are commonly used in asynchronous programming in Node.js to handle tasks that take time to complete.

• They are passed as arguments to functions that will call them once a certain task is completed.

• Callback functions can be used to handle the result of an asynchronous operation, such as reading a file or making an HTTP request.

• Example:...read more

Closures are functions that have access to their own scope, as well as the scope in which they were defined.

• Closures allow functions to access variables from their outer scope even after the outer function has finished executing.

• They are commonly used in event handlers, callbacks, and in functional programming.

• Example: const outerFunction = () => { const outerVar = 'I am outer'; return () => { console.log(outerVar); }; }; const innerFunction = outerFunction(); innerFunction()...read more

Hoisting is a JavaScript mechanism where variable and function declarations are moved to the top of their containing scope during compilation.

• Variable and function declarations are hoisted to the top of their scope.

• Only declarations are hoisted, not initializations.

• Function declarations take precedence over variable declarations.

JavaScript is a high-level, interpreted programming language used for creating interactive websites and web applications.

• JavaScript is often used for client-side scripting to make web pages interactive.

• It can also be used for server-side development with Node.js.

• JavaScript is versatile and can be used for creating games, mobile apps, and more.

var is function scoped, let and const are block scoped.

• var can be redeclared and updated within its scope

• let can be updated but not redeclared within its scope

• const cannot be updated or redeclared once declared

• let and const are not hoisted like var

• const must be initialized during declaration

Microservices architecture is an architectural style that structures an application as a collection of loosely coupled services.

• Each service is self-contained and can be developed, deployed, and scaled independently.

• Services communicate with each other over lightweight protocols like HTTP or messaging queues.

• Microservices allow for flexibility, scalability, and resilience in large and complex applications.

• Examples of companies using microservices architecture include Netflix,...read more

API Gateway in AWS is a fully managed service that makes it easy for developers to create, publish, maintain, monitor, and secure APIs at any scale.

• API Gateway allows you to create RESTful APIs that can be integrated with other AWS services like Lambda, DynamoDB, and S3.

• It provides features like authentication, authorization, rate limiting, and caching to improve API performance and security.

• API Gateway can also be used to transform and proxy requests to different backend ser...read more

NPM (Node Package Manager) is a package manager for Node.js that allows developers to easily install, manage, and share packages of code.

• NPM is used to install and manage dependencies for Node.js projects.

• It comes pre-installed with Node.js and allows developers to easily add external libraries and tools to their projects.

• NPM uses a file called package.json to keep track of project dependencies and metadata.

• Developers can also publish their own packages to the NPM registry fo...read more