Rigi React Js Frontend Developer Interview Questions and Answers

Create a photo galary using flatList

Q1. Basic JS question event loop, promises, polyfill.
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Q2. JS output based, Flatten object.
Ans. 
Flattening an object involves converting nested objects into a single-level object with concatenated keys.
• Use recursion to traverse nested objects and build a flat object.

• Example: { a: { b: 1, c: 2 }, d: 3 } becomes { 'a.b': 1, 'a.c': 2, d: 3 }.

• Utilize a helper function to manage key concatenation during traversal.

• Consider edge cases like arrays or null values in the object.
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The first round consisted of a coding exercise along with fundamental questions related to React Native, JavaScript, and inquiries about objects and arrays.

Q1. Native modules, useRef, Flatlist
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Q1. Javascript basics
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Q1. React native basics
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Q2. Scroll vs flatlist
Ans. 
FlatList is more efficient for rendering large lists with better performance compared to ScrollView.
• FlatList is optimized for rendering long lists by only rendering the items that are currently visible on the screen.

• ScrollView renders all of its children at once, which can lead to performance issues with large lists.

• FlatList also provides built-in support for pull-to-refresh, infinite scrolling, and item separators.

• Scr...read more
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Q3. Design carousel in react native
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Designing a carousel in React Native involves creating a horizontal scroll view with swipe functionality.
• Use ScrollView component with horizontal prop to create the carousel layout.

• Render multiple items inside the ScrollView to display carousel content.

• Implement swipe gestures to navigate between carousel items.

• Consider using libraries like 'react-native-snap-carousel' for additional features and customization.
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The first round is Hackerrank two algo and one UI test very easy, Second is Fundamentals of JS and React Native one must have a deep understanding of JS to do that I strongly suggest going through Akashay Saini's JS series It'll help and the Third is PS/DS asked some basic A&DS questions can be solved easily with little practice on Leetcode

Round duration - 45 Minutes
Round difficulty - Medium

It was in the mid day and since I applied for a Frontend role the discussion was majorly around data structure and bit of Javascript.
The interviewer was helping and good listener.

Q1. 
Merge Two Sorted Linked Lists Problem Statement
You are provided with two sorted linked lists. Your task is to merge them into a single sorted linked list and return the head of the combined linked list.
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Ans. 
Merge two sorted linked lists into a single sorted linked list without using additional space.
• Create a dummy node to start the merged list

• Compare the values of the two linked lists and add the smaller value to the merged list

• Move the pointer of the merged list and the pointer of the smaller value list

• Continue this process until one of the lists is fully traversed

• Append the remaining elements of the other list to the me...read more
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Q2. 
Sort 0 1 2 Problem Statement
Given an integer array arr of size 'N' containing only 0s, 1s, and 2s, write an algorithm to sort the array.
Input:
The first line contains an integer 'T' representing the n...read more
Ans. 
Sort an array of 0s, 1s, and 2s in linear time complexity.
• Use three pointers to keep track of 0s, 1s, and 2s while traversing the array.

• Swap elements based on the values encountered to sort the array in-place.

• Time complexity should be O(N) and space complexity should be O(1).
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Round duration - 60 Minutes
Round difficulty - Medium

It was more of a in depth round on the framework I'm working on and problem solving.

Q1. What is the event loop and what is its significance?
Ans. 
The event loop is a mechanism in programming that allows for asynchronous execution of code.
• The event loop is a key component in JavaScript's runtime environment, responsible for handling asynchronous operations.

• It continuously checks the call stack for any pending tasks and executes them in a non-blocking manner.

• The event loop ensures that the program remains responsive by allowing other code to run while waiting for ...read more
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Q2. Can you provide examples of output-based questions in JavaScript that utilize browser APIs?
Ans. 
Output-based questions in JavaScript using browser APIs
• Example 1: Write a script that uses the Geolocation API to display the user's current location on a map

• Example 2: Create a program that uses the Web Audio API to play a sound when a button is clicked

• Example 3: Develop a web page that uses the Canvas API to draw a simple animation
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Q3. How would you design a system to support localization in a mobile app?
Ans. 
Designing a system to support localization in a mobile app
• Use resource files to store localized strings for different languages

• Implement a language selection feature for users to choose their preferred language

• Utilize localization libraries or frameworks to streamline the process

• Consider cultural differences when localizing content, such as date formats and currency symbols
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Round duration - 75 Minutes
Round difficulty - Hard

It was more of a fitment/managerial round.
Didn't had any coding questions, but was asked more on approaches and optimisations.
Discussions on the project you have worked on.

Q1. You need to find the fastest 3 horses out of a group, given that you can only race 5 horses at a time. How would you approach this problem?
Ans. 
To find the fastest 3 horses out of a group with 5 horses racing at a time, we can use a tournament style approach.
• Divide the horses into groups of 5 and race them against each other. This will give you the fastest horse in each group.

• Take the winners from each group and race them against each other. The top 3 horses in this final race will be the fastest 3 overall.

• Keep track of the results and compare the timings to d...read more
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Q2. How do you debug the root cause of lag on a screen?
Ans. 
To debug lag on a screen, analyze code, check for memory leaks, optimize rendering, and use profiling tools.
• Analyze code to identify any inefficient algorithms or operations causing lag.

• Check for memory leaks that could be impacting performance.

• Optimize rendering by reducing the number of draw calls, optimizing shaders, and minimizing overdraw.

• Use profiling tools like Xcode Instruments or Android Profiler to identify p...read more
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Q3. Can you explain the architecture of the app you have recently worked on?
Ans. 
The app I recently worked on is a social media platform for sharing photos and connecting with friends.
• The app follows a client-server architecture, with the client being the mobile app and the server handling data storage and processing.

• The client side is built using React Native for cross-platform compatibility.

• The server side is implemented using Node.js with a MongoDB database for storing user data and photos.

• The a...read more
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