bebo Technologies Reactjs Developer Interview Questions and Answers

Q1. What is Event loop
Ans. 
Event loop is a mechanism in JavaScript that allows for asynchronous operations to be executed in a non-blocking way.
• Event loop is responsible for handling asynchronous operations in JavaScript.

• It allows for non-blocking execution of code by moving asynchronous tasks to the event queue.

• Event loop continuously checks the call stack and the event queue, moving tasks from the queue to the stack when the stack is empty.

• Exa...read more
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Q2. What are closures
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Closures are functions that have access to their own scope, as well as the scope in which they were defined.
• Closures allow functions to access variables from their outer scope even after the outer function has finished executing.

• They are commonly used to create private variables in JavaScript.

• Closures are created whenever a function is defined within another function.
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Q1. Basic reactjs Questions with some javascript coding snippets
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Q1. Basics of Javascript
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Q2. Basics of React
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Q1. Difference between promise and async await ?
Ans. 
Promises are objects representing the eventual completion or failure of an asynchronous operation, while async/await is a syntactic sugar built on top of promises to write asynchronous code in a synchronous manner.
• Promises are used to handle asynchronous operations and provide a way to chain multiple asynchronous operations together.

• Async/await allows you to write asynchronous code that looks synchronous, making it eas...read more
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Q2. Event loop based a console output questions?
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Q3. UseMemo vs useCallback
Ans. 
useMemo is used for memoizing expensive calculations, while useCallback is used for memoizing functions.
• useMemo is used to memoize expensive calculations and only recompute the value when the dependencies change.

• useCallback is used to memoize functions and only re-create the function when the dependencies change.

• Example: useMemo can be used to memoize the result of a complex computation, while useCallback can be used t...read more
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Q1. Difference beetween thow and new thow
Ans. 
throw is used to throw an exception, new throw is used to throw an exception with a new object
• throw is used to throw an exception in JavaScript

• new throw is used to throw an exception with a new object

• Example: throw new Error('Something went wrong')
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Q2. How to add validation
Ans. 
Validation in React can be added using form validation libraries, custom validation functions, or built-in HTML5 validation attributes.
• Use form validation libraries like Formik or Yup for easy validation setup

• Create custom validation functions to validate input fields based on specific requirements

• Utilize built-in HTML5 validation attributes like required, pattern, and min/max for basic validation

• Display error messages...read more
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Q1. Routing concept
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Q2. React js coding question
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Q1. What is difference between get props and set props
Ans. 
get props is used to retrieve the value of a property in React components, while set props is used to update the value of a property.
• get props is used to access the value of a property passed down from a parent component

• set props is used to update the value of a property in the current component

• Example: get props - accessing the 'name' prop in a child component: this.props.name

• Example: set props - updating the 'count' ...read more
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Q2. What is difference between get for each and map
Ans. 
get forEach is used to iterate over elements in an array without returning a new array, while map creates a new array by applying a function to each element.
• forEach does not return a new array, while map returns a new array with the results of applying a function to each element

• forEach is used for side effects, while map is used for transforming data

• forEach does not return anything, while map returns a new array

• Example...read more
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Q3. Difference between put and patch
Ans. 
PUT is used to update or replace an entire resource, while PATCH is used to update or modify part of a resource.
• PUT is idempotent, meaning multiple identical requests will have the same effect as a single request.

• PATCH is not necessarily idempotent, as multiple identical requests may have different effects.

• PUT requires the client to send the entire updated resource, while PATCH only requires the client to send the spec...read more
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Q4. Difference between local storage session storage
Ans. 
Local storage is persistent and stays until manually cleared, while session storage is temporary and cleared when the browser is closed.
• Local storage data persists even after closing the browser

• Session storage data is cleared when the browser is closed

• Both store data as key-value pairs similar to cookies
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