Synechron React Js Frontend Developer Interview Questions and Answers

Q1. What is the difference between debounce and throttling
Ans. 
Debounce delays the execution of a function until after a specified time period, while throttling limits the rate at which a function can be executed.
• Debounce waits for a specified time period of inactivity before executing the function, while throttling limits the rate at which the function can be called.

• Debounce is useful for scenarios like search bars where you want to wait for the user to finish typing before makin...read more
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Q2. What was used before Rest APIs
Ans. 
SOAP (Simple Object Access Protocol) was used before Rest APIs for web services communication.
• SOAP was a protocol for exchanging structured information in the implementation of web services.

• SOAP used XML for message format and relied heavily on HTTP for communication.

• SOAP was more rigid and complex compared to Rest APIs, which are more lightweight and flexible.

• Examples of SOAP-based web services include Microsoft's .NE
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Q1. Uncontrolled components
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Q2. Why to use uncontrolled components instead of controlled
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Q1. Object , array , ES6, React basics
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Q1. Advance Javascript questions
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Q2. React application with custom hooks
Ans. 
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
Ans. 
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
Ans. 
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
Ans. 
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
Ans. 
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
Ans. 
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
Ans. 
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
Ans. 
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 me about your self
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What is react , feature, axios, API

Redux Redux toolkit Redux thunk

Q1. Questions on JavaScript and React js
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Q1. 1) State and props 2) Basic JS question
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