Techtree Technologies React Js Frontend Developer Interview Questions and Answers

What is React? What is React architecture ? What is dynamic imports? What is interceptor?

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. 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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React js Assessments

Q1. DSA related to binary search
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Q1. System Design for elevator
Ans. 
System design for elevator
• Consider the number of floors in the building

• Think about the capacity of the elevator

• Design algorithms for efficient movement of the elevator

• Include safety features such as emergency stop

• Consider user interface for passengers
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Q1. 1) State and props 2) Basic JS question
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Q1. What is Redux ? How we are using it in real time
Ans. 
Redux is a predictable state container for JavaScript apps.
• Redux is a state management library for JavaScript applications.

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

• Redux stores the entire state of the application in a single immutable object.

• Actions are dispatched to update the state, and reducers specify how the state changes in response to actions.

• Redux is commonly used with React to man...read more
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Q2. What is Virtual Dom ? and its work in reactjs
Ans. 
Virtual DOM is a lightweight copy of the actual DOM in memory, used by React to improve performance by minimizing actual DOM manipulations.
• Virtual DOM is a concept where a lightweight copy of the actual DOM is kept in memory.

• React uses Virtual DOM to improve performance by minimizing actual DOM manipulations.

• When state changes in a React component, a new Virtual DOM representation is created and compared with the previ...read more
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Q3. What is difference in usememo and react.memo
Ans. 
useMemo is used for memoizing expensive calculations, while React.memo is used for memoizing functional components.
• useMemo is a hook used to memoize expensive calculations and only recompute the value when the dependencies change.

• React.memo is a higher order component used to memoize functional components and prevent unnecessary re-renders.

• useMemo is typically used for optimizing performance by caching values, while Re...read more
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Q4. Difference between map and forEach ?
Ans. 
map returns a new array with modified elements, forEach does not return anything and just iterates over the array.
• map returns a new array with the results of calling a provided function on every element in the array.

• forEach executes a provided function once for each array element without returning anything.

• Example: const numbers = [1, 2, 3]; const doubled = numbers.map(num => num * 2); // doubled will be [2, 4, 6]; num...read more
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Q5. Find Duplicacy Array
Ans. 
Find duplicates in an array of strings
• Iterate through the array and use a hash map to keep track of the frequency of each element

• If an element is already in the hash map, it is a duplicate
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Q6. What is Currying function ?
Ans. 
Currying is a technique in functional programming where a function with multiple arguments is transformed into a sequence of functions, each taking a single argument.
• Currying helps in creating reusable functions and improving code readability.

• It allows partial application of functions, where some arguments are fixed and others are left to be provided later.

• Example: const add = (a) => (b) => a + b; add(2)(3) will return
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