Techolution React Native Developer Interview Questions and Answers

Q1. What is enums in typescript, difference between shallow and deep copy, what is virtual dom, what are closures, some psuedo codes, react machine coding. and other basic javascript questions.
Ans. 
Enums in TypeScript are a way to define a set of named constants. Shallow copy only copies the reference, while deep copy creates a new object. Virtual DOM is a lightweight copy of the actual DOM. Closures are functions that have access to their own scope and the scope of their containing function.
• Enums in TypeScript are used to define a set of named constants. For example, enum Color { Red, Green, Blue }

• Shallow copy c...read more
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Q1. Testing related questions, and other javascript and react questions.
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Q1. What are the different android components and concepts such as Recycler View, View Model, ANR and how do they function internally?
Ans. 
Android components like Recycler View, View Model, ANR are essential for building robust Android applications.
• Recycler View: Efficient way to display large data sets by recycling views as they scroll off the screen.

• View Model: Manages UI-related data in a lifecycle-conscious way, surviving configuration changes.

• ANR (Application Not Responding): Dialog shown to the user when the main thread of an app is blocked for too ...read more
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Q2. How will you debug and solve the following crash and ANR from the given stack trace?
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Q3. Solve this DSA question.
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Q1. Similar questions to the first round.
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Q1. Implement an LRU cache
Ans. 
LRU cache is a data structure that stores the most recently used items, discarding the least recently used items when full.
• Use a hashmap to store key-value pairs for quick access

• Use a doubly linked list to keep track of the order of items based on their usage

• When an item is accessed, move it to the front of the list

• When the cache is full, remove the least recently used item from the end of the list
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Q1. Asked json web tokean authentication, authorisation. architecture of your project.
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Q2. Coding question- create crud app. Given array of objects. Render list in table. Do edit, delete, sort list on object property.
Ans. 
Create a CRUD app to render, edit, delete, and sort a list of objects in a table.
• Create a React component to render a table with data from the array of objects.

• Implement functions for editing and deleting objects from the list.

• Add functionality to sort the list based on object properties.

• Use state and props to manage data and re-render the table when changes occur.
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Q3. Difference bw rem, em, px. React hooks- useEffect, life cycle methods. use cases of hooks.
Ans. 
rem, em, px are units of measurement in CSS. useEffect is a React hook for side effects. Hooks are used for stateful logic in functional components.
• rem: relative to the font-size of the root element (html). Example: 1rem = 16px

• em: relative to the font-size of the element. Example: 2em = 32px if the font-size of the element is 16px

• px: fixed-size units. Example: font-size: 14px

• useEffect: React hook used for side effects ...read more
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Q1. Activity life cycle Factorial and fabbonacci series lateiniti var vs lazy Var vs val
Ans. 
Activity life cycle is a crucial concept in Android development. Factorial and Fibonacci series are common mathematical problems. lateinit var and lazy are used for initializing variables. Var and val are used for declaring variables.
• Activity life cycle includes methods like onCreate, onStart, onResume, onPause, onStop, onDestroy.

• Factorial is the product of all positive integers up to a given number. Example: 5! = 5*4*...read more
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There were total 3 rounds and it consists of Basic array and string coding question

Q1. Life Cycle Methods off class components
Ans. 
Life cycle methods are special methods in class components that allow developers to run code at specific points in the component's life cycle.
• componentDidMount() is called after the component has been rendered to the DOM.

• componentDidUpdate() is called after the component's state or props have been updated.

• componentWillUnmount() is called before the component is removed from the DOM.
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Q2. Diffrence between FlatList and ScrollView
Ans. 
FlatList is optimized for rendering large lists efficiently by only rendering the items that are currently visible, while ScrollView renders all of its children at once.
• FlatList is more performant for long lists as it only renders 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 datasets.

• FlatList supports key extraction fo...read more
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Q3. Real World Scenories Questions
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Q1. Java Script coding question
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Round duration - 60 minutes
Round difficulty - Easy

This was a DSA based round, I was asked to code on collabedit.

Q1. 
Rearrange Linked List Problem Statement
Given a singly linked list in the form 'L1' -> 'L2' -> 'L3' -> ... 'Ln', your task is to rearrange the nodes to the form 'L1' -> 'Ln' -> 'L2' -> '...read more
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Q2. 
Find Missing Number In String Problem Statement
You have a sequence of consecutive nonnegative integers. By appending all integers end-to-end, you formed a string S without any separators. During this pro...read more
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Q3. 
Palindrome Permutation - Problem Statement
Determine if a permutation of a given string S can form a palindrome.
Example:
Input:
string S = "aab"
Output:
"True"
Explanation:
The permutation "aba" o...read more
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Round duration - 30 minutes
Round difficulty - Medium

This was onsite interview round 1. Java and Android threading concepts are needed.

Q1. What is a Cyclic Barrier in Java?
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Q2. What are the different launch modes for activities in Android?
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Q3. How can you pass a simple Java object from one thread to another?
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Round duration - 60 minutes
Round difficulty - Easy

This round was all about android and internals of collections in Java.

Q1. What is an IntentService?
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Q2. What is the difference between deep links and app links?
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Q3. What are the IPC mechanisms available in Android OS?
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Round duration - 90 minutes
Round difficulty - Medium

Technical interview round for purely checking the design knowledge of a person.

Q1. 
LRU Cache Design Question
Design a data structure for a Least Recently Used (LRU) cache that supports the following operations:
1. get(key) - Return the value of the key if it exists in the cache; otherw...read more
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Q2. How would you design an ImageDownloader that efficiently handles parallel API calls?
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Round duration - 30 minutes
Round difficulty - Easy

This was the last Interview with director of engineering.