30+ Node JS Developer Interview Questions and Answers for Freshers

The main modules of Node.js are HTTP, File System, Path, and Events.

• HTTP module allows Node.js to transfer data over the HyperText Transfer Protocol (HTTP).

• File System module enables interaction with the file system, allowing reading, writing, and manipulating files.

• Path module provides utilities for working with file and directory paths.

• Events module allows for event-driven programming, enabling the creation and handling of custom events.

Node.js is a JavaScript runtime built on Chrome's V8 JavaScript engine, used for server-side and networking applications.

• Node.js is an open-source, cross-platform runtime environment for executing JavaScript code outside of a browser.

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

• Node.js allows developers to build scalable and high-performance applications.

• It provides a rich set of built-in modules and libraries for various functionali...read more

Node.js uses event-driven architecture to handle asynchronous tasks while synchronous tasks are executed in a blocking manner.

• Node.js uses event loop to handle asynchronous tasks by offloading them to the system, allowing other tasks to continue without waiting.

• Synchronous tasks are executed in a blocking manner, meaning the program waits for each task to complete before moving on to the next one.

• Node.js provides non-blocking I/O operations which allow multiple tasks to be ex...read more

NodeJs is a JavaScript runtime built on Chrome's V8 JavaScript engine. ServerSide is a term used to describe code that runs on the server side. Redux is a predictable state container for JavaScript apps. Flex is a CSS layout model. Mongo is a NoSQL database. Express is a web application framework for Node.js.

• NodeJs is a runtime environment that allows you to run JavaScript on the server side.

• ServerSide refers to code that is executed on the server rather than the client side....read more

Public, private, and protected are access modifiers used in object-oriented programming to control the visibility of class members.

• Public: accessible from outside the class

• Private: only accessible within the class

• Protected: accessible within the class and its subclasses

Node.js is used for its non-blocking, event-driven architecture. It is single-threaded to optimize performance.

• Node.js is popular for its asynchronous, non-blocking I/O model which allows for handling multiple requests efficiently.

• Being single-threaded, Node.js can handle a large number of connections without the overhead of creating a new thread for each request.

• Node.js uses event-driven architecture and callbacks to handle requests, making it highly scalable and performant....read more

I deploy my application using containerization and continuous integration/continuous deployment (CI/CD) pipelines.

• Utilize Docker to containerize the application for easy deployment and scalability

• Use CI/CD pipelines such as Jenkins or GitLab CI to automate the deployment process

• Deploy to cloud platforms like AWS, Azure, or Google Cloud for reliable hosting

• Implement monitoring and logging tools like Prometheus and ELK stack for performance tracking

apply, call, and bind are methods used to manipulate the context of a function in JavaScript.

• apply() - calls a function with a given 'this' value and arguments provided as an array

• call() - calls a function with a given 'this' value and arguments provided individually

• bind() - creates a new function that, when called, has its 'this' keyword set to the provided value

Fork creates a new process while spawn launches a new process asynchronously.

• Fork is used to create child processes in Node.js, typically for running separate instances of the same application.

• Spawn is used to launch a new process asynchronously, allowing for communication between the parent and child processes.

• Fork is commonly used in cluster mode for load balancing in Node.js applications.

• Spawn is used for executing external commands or scripts in Node.js.

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

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() {}

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

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 simultaneously without blocking the execution of other code.

• Event loop continuously checks the event queue for new events and executes them in a non-blocking manner.

• Node.js uses event-driven architecture, where callbacks are executed when events occur.

• Example: ...read more

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.

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

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

Asynchrony is the ability of a system to handle multiple tasks concurrently without blocking the main thread.

• Asynchrony allows tasks to run independently of each other, improving performance and responsiveness.

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

• Examples of asynchronous operations in Node.js include reading files, making network requests, and executing database queries.

The split() method is used to split a string into an array of substrings based on a specified separator.

• The split() method takes a separator as an argument, which can be a string or a regular expression.

• The method returns an array of substrings created by splitting the original string at each occurrence of the separator.

• Example: 'hello world'.split(' ') will return ['hello', 'world']

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

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

• Only declarations are hoisted, not initializations.

• Function declarations take precedence over variable declarations.

Deep copy is a copy of an object that duplicates all of its properties and nested objects, creating a new independent copy.

• Deep copy creates a new object with all properties and nested objects copied.

• Changes made to the original object do not affect the deep copy.

• Deep copy is often used when you need to modify an object without affecting the original.

Callbacks are functions passed as arguments to other functions, to be executed later.

• Callbacks are commonly used in asynchronous programming in Node.js.

• They allow functions to be executed after another function has finished its execution.

• Callbacks can be used to handle events, make API calls, or perform other tasks asynchronously.

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

Closures are functions that have access to variables from their outer scope even after the outer function has finished executing.

• Closures allow functions to access variables from their parent function even after the parent function has returned.

• They help in maintaining state in JavaScript.

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

Promises in Node.js are objects representing the eventual completion or failure of an asynchronous operation.

• Promises are used to handle asynchronous operations in a more readable and manageable way.

• They can be in one of three states: pending, fulfilled, or rejected.

• Promises can be chained together using .then() to handle success or failure.

• They help avoid callback hell and make code more maintainable.

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

Inheritance is a concept in object-oriented programming where a class inherits properties and behaviors from another class.

• Inheritance allows a class to reuse code from another class, promoting code reusability and reducing redundancy.

• The class that is being inherited from is called the parent class or superclass, while the class that inherits is called the child class or subclass.

• Child classes can add new properties and methods, or override existing ones from the parent clas...read more

Handling a critical production issue with multiple dependencies failing

• Identify the root cause of the issue by analyzing logs and code

• Communicate effectively with team members and stakeholders to coordinate a solution

• Implement a temporary fix if necessary to minimize impact on users

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

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

• It allows Node.js to perform non-blocking I/O operations efficiently.

• Event loop continuously checks the event queue for any pending events to be processed.

• It helps in managing the flow of code execution in an asynchronous environment.

• Example: setTimeout() function in Node.js uses event loop to sch...read more