Nagarro Senior Node Js Developer Interview Questions and Answers

Q1. Object , array , ES6, React basics
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Q1. Advance Javascript questions
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Q2. React application with custom hooks
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Custom hooks in React allow for reusable logic across components.
• Custom hooks are functions that use React hooks internally and can be reused across multiple components.

• They can encapsulate complex logic and state management, making components more modular and easier to maintain.

• Example: A custom hook for fetching data from an API and handling loading and error states can be used in multiple components.

• Example: A custo...read more
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Q1. Roles & Responsibilites
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Q1. Types of Promises
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Promises in JavaScript are objects representing the eventual completion or failure of an asynchronous operation.
• Promises can be in one of three states: pending, fulfilled, or rejected.

• Promises can be chained using .then() to handle success and .catch() to handle errors.

• Promises can be created using the Promise constructor or by using async/await syntax.
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Q2. Difference between useState and useEffect
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useState is used to manage state in functional components, while useEffect is used to perform side effects in functional components.
• useState is used to declare state variables in functional components.

• useEffect is used to perform side effects in functional components, such as data fetching, subscriptions, or manually changing the DOM.

• useState does not trigger re-renders, while useEffect can be used to trigger re-render...read more
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Q3. What is Callback hell
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Callback hell is a situation 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 understand

• Can be avoided by using Promises, async/await, or modularizing code
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Q4. Difference between traditional function and arrow function
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Traditional functions are defined using the function keyword, while arrow functions are defined using a concise syntax with =>.
• Traditional functions are hoisted, while arrow functions are not.

• Arrow functions do not have their own 'this' keyword, they inherit it from the parent scope.

• Arrow functions are more concise and easier to read compared to traditional functions.

• Traditional functions are better for methods in obje...read more
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Q5. Usecase to create counter in react
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Creating a counter in React to increment and decrement a value.
• Create a state variable to store the count value

• Use setState to update the count value

• Render the count value in the component

• Add buttons to increment and decrement the count value
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Q6. Program to find frequency of letters in a string
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Program to find frequency of letters in a string
• Create an object to store the frequency of each letter

• Loop through the string and increment the count of each letter in the object

• Convert the object into an array of strings with letter and frequency pairs
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Q7. Program to find if substring is present in a given string without using predefined functions
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Iterate through the given string to check if the substring is present.
• Iterate through the given string and check if each character matches the first character of the substring.

• If a match is found, check the subsequent characters to see if they form the substring.

• Return true if the entire substring is found within the given string, otherwise return false.
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Q1. Basic React question
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Q2. Few Javascript questions
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Q1. Tell be about yourself
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Q2. Skills questions
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Q1. Online Quiz in My Skills
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Q1. Tell me about your self
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What is react , feature, axios, API

Redux Redux toolkit Redux thunk

Q1. Uncontrolled components
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Q2. Why to use uncontrolled components instead of controlled
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Q1. Questions on JavaScript and React js
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Q1. What is nodejs, explain the event loop.
Ans. 
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 ...read more
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Q2. What is event loop ?
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Event loop is a mechanism that allows Node.js to perform non-blocking I/O operations.
• Event loop is a single-threaded loop that constantly checks for new events in the event queue.

• It executes the callback functions associated with the events in the queue.

• It allows Node.js to handle multiple requests simultaneously without blocking the execution of other requests.

• It is responsible for managing the order of execution of t...read more
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Q3. What is the role of libuv ?
Ans. 
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,
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Q1. What is the difference between cluster and thread ?
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Cluster is a group of processes that share the same resources while thread is a lightweight process that shares the same memory.
• Cluster is used for scaling and load balancing while thread is used for improving performance.

• Cluster can run on multiple machines while thread runs within a single process.

• Cluster requires inter-process communication while thread does not.

• Examples of cluster include PM2 and Node.js cluster mo...read more
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