Pristyn Care Front end Developer Interview Questions and Answers

Q1. What is denbouncer and throttle
Ans. 
Debouncer and throttle are techniques used to limit the frequency of function calls.
• Debouncing delays the execution of a function until a certain amount of time has passed without the function being called again.

• Throttling limits the frequency of function calls to a certain rate, executing the function at fixed intervals.

• Debouncing is useful for events that may be triggered multiple times in quick succession, such as r...read more
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Q2. What is curry function
Ans. 
Currying is a technique of transforming a function that takes multiple arguments into a sequence of functions that each take a single argument.
• Currying allows partial application of a function

• It helps in creating reusable functions

• Curried functions are easier to compose and chain

• Example: const add = (a) => (b) => a + b; add(2)(3) returns 5
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Q3. Implement curry function
Ans. 
Curry function is a higher-order function that allows partial application of arguments.
• Currying transforms a function that takes multiple arguments into a series of functions that take one argument each.

• It returns a new function until all the arguments are received and then executes the original function.

• Example: const add = (a, b) => a + b; const curriedAdd = curry(add); curriedAdd(2)(3) returns 5.
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Q4. What is promise.all()
Ans. 
promise.all() is a method that takes an array of promises and returns a new promise that resolves when all promises in the array have resolved.
• It is used to handle multiple asynchronous operations simultaneously.

• If any of the promises in the array rejects, the returned promise will be rejected with the reason of the first rejected promise.

• The resolved values of the promises are returned as an array in the same order as
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Q5. What is memoization?
Ans. 
Memoization is a technique of caching the results of a function to improve performance.
• Memoization is used to avoid redundant calculations by storing the results of a function and returning the cached result when the same inputs occur again.

• It is commonly used in recursive functions and functions with expensive computations.

• Memoization can be implemented manually or by using libraries like Lodash or Memoizee.

• Example: M...read more
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Q6. What is closure in javascript
Ans. 
Closure is a function that has access to its parent scope even after the parent function has returned.
• Closure allows for private variables and functions in JavaScript.

• It is created when a function returns another function.

• The inner function has access to the outer function's variables and parameters.

• Example: function outer() { let x = 10; return function inner() { console.log(x); } }

• The inner function can access and mo...read more
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Q7. What is the problem with colosures
Ans. 
Closures can cause memory leaks if not handled properly.
• Closures can hold references to variables outside of their scope, preventing them from being garbage collected.

• If closures are used excessively or not released properly, they can cause memory leaks.

• To avoid memory leaks, make sure to release closures when they are no longer needed.
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Q8. Some output questions on SetTimeout to check closure knowledge
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Q9. React lifecycle events
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Q10. Major difference between class based components and class based components
Ans. 
There is no difference between class based components and class based components.
• There seems to be a typo in the question.

• Assuming the question is about functional components vs class components, the major difference is that class components use a class to define the component while functional components are defined as functions.

• Class components have access to lifecycle methods while functional components do not.

• Functi...read more
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Q11. Shallow copy vs deep copy
Ans. 
Shallow copy only copies the reference to an object while deep copy creates a new object with a new memory address.
• Shallow copy is faster and uses less memory than deep copy.

• In shallow copy, changes made to the original object will reflect in the copied object as well.

• Deep copy creates a completely new object with its own memory space.

• In JavaScript, arrays and objects are assigned by reference, so a shallow copy will o...read more
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Q12. How to do deep copy ?
Ans. 
Deep copy creates a new object with the same values as the original object.
• Use Object.assign() method to create a deep copy of an object.

• For nested objects, use recursion to copy all levels.

• For arrays, use slice() method to create a new array with the same values.

• Avoid using spread operator for deep copy as it only creates a shallow copy.
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Q13. What is hoisting? Some questions on it
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Round duration - 60 Minutes
Round difficulty - Easy

Q1. 
0/1 Knapsack Problem Statement
A thief is planning to rob a store and can carry a maximum weight of 'W' in his knapsack. The store contains 'N' items where the ith item has a weight of 'wi' and a value of...read more
Ans. 
Yes, the 0/1 Knapsack problem can be solved using dynamic programming with a space complexity of not more than O(W).
• Use a 1D array to store the maximum value that can be stolen for each weight capacity from 0 to W.

• Iterate through each item and update the array based on whether including the item would increase the total value.

• The final value in the array at index W will be the maximum value that can be stolen.
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Q2. 
Find the Second Largest Element
Given an array or list of integers 'ARR', identify the second largest element in 'ARR'.
If a second largest element does not exist, return -1.
Example:
Input:
ARR = [2,...read more
Ans. 
Find the second largest element in an array of integers.
• Iterate through the array to find the largest and second largest elements.

• Handle cases where all elements are identical.

• Return -1 if a second largest element does not exist.
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Round duration - 60 Minutes
Round difficulty - Easy

System Design Round

Q1. Design a system for Twitter, discussing its architecture, key components, and scalability considerations.
Ans. 
Design a scalable system for Twitter with key components and architecture.
• Use microservices architecture for scalability and fault isolation.

• Key components include user service, tweet service, timeline service, and notification service.

• Use a distributed database like Cassandra for storing tweets and user data.

• Implement a message queue like Kafka for handling real-time updates and notifications.

• Use a caching layer like ...read more
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Round duration - 30 Minutes
Round difficulty - Easy

It is just a formality

Duration 1Hr
2 coding questions

Q1. Don't remember the questions
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Q2. Don't remember the questions.
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Q1. The question was about Nodejs
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Q2. The question was to build a linked list in Nodejs
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Q1. The first question was related to DSA
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Q2. The question was related to SQL
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Basic coding only not to worry much

Q1. Tell me about ur self
Ans. 
I am a passionate software developer with experience in Java, Python, and web development.
• Experienced in Java, Python, and web development technologies

• Strong problem-solving skills

• Excellent team player with good communication skills
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Q2. What is ur projects
Ans. 
I have worked on various projects including a web-based inventory management system and a mobile app for tracking fitness goals.
• Developed a web-based inventory management system using React and Node.js

• Created a mobile app for tracking fitness goals using Flutter

• Implemented RESTful APIs for communication between frontend and backend systems
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Sorting of an array and aptitude

Q1. BFS graph traversal
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Q1. Binary tree question
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Easy level to Medium level

2 Easy questions of DSA

Q1. One DSA question
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Q2. Normal discussion about tech stack
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Q1. Tell about yourself
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Q2. Why do you want to join digit?
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