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 single-threaded, but can handle multiple threads using child processes or worker threads.

• Use child processes to run multiple instances of Node.js

• Use worker threads for CPU-intensive tasks

• Leverage the cluster module to create a pool of worker processes

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

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

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.

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() {}

The Fibonacci series is a sequence where each number is the sum of the two preceding ones, starting from 0 and 1.

• Definition: The Fibonacci series starts with 0 and 1, and each subsequent number is the sum of the previous two (e.g., 0, 1, 1, 2, 3, 5, 8, ...).

• Recursive Approach: A simple way to generate Fibonacci numbers is through recursion, where the function calls itself to calculate the next number.

• Iterative Approach: An iterative method uses loops to calculate Fibonacci nu...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.

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

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

Time work hour refers to the hours during which an employee is expected to perform their job duties.

• Typically, a standard work hour is 8 hours a day, 40 hours a week.

• Work hours can vary based on the industry; for example, healthcare may require shifts.

• Flexible work hours allow employees to choose their start and end times.

• Overtime refers to hours worked beyond the standard work hours, often compensated at a higher rate.

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.

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']

Piping in Node.js allows data to flow from one stream to another, enabling efficient data processing.

• Piping connects a readable stream to a writable stream using the `.pipe()` method.

• Example: `readableStream.pipe(writableStream)` transfers data from the readable stream to the writable stream.

• Piping is useful for handling file uploads, downloads, and data transformations.

• It automatically manages backpressure, ensuring that the writable stream does not get overwhelmed.

• Common us...read more

Creating a pyramid pattern in JavaScript involves using loops to print spaces and asterisks in a structured format.

• Use a for loop to iterate through the number of rows.

• For each row, print spaces to align the pyramid shape.

• Print asterisks based on the current row number.

• Example: For 5 rows, the output will be: * *** ***** ******* *********

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

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.

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.

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) => { ... });